aiskillstore/music-generation

Quick Start (Read This First!)

IMPORTANT: This file is located at /mnt/skills/private/music-generation/SKILL.md

If you need to reference this skill again during your session, read that exact path directly. Do not explore directories or use find commands - just read the file path above.

Philosophy

This skill provides tools and patterns for music composition, not pre-baked solutions. You should use your intelligence and the music21 library to compose dynamically based on user requests.

Core Principle: Write custom code that composes music algorithmically rather than calling functions with hardcoded melodies.

Installation & Setup

Quick Installation

Run the automated installer for complete setup:

bash
bash /mnt/skills/private/music-generation/install.sh

This installs all system dependencies, Python packages, and verifies the installation.

Note: The install script may display "error: externally-managed-environment" messages at the end. These are expected and can be safely ignored - the dependencies are already installed. If you see these messages, the installation was successful.

Manual Installation

Alternatively, install dependencies manually:

System Dependencies:

bash
apt-get update
apt-get install -y fluidsynth fluid-soundfont-gm fluid-soundfont-gs ffmpeg

Python Dependencies:

bash
pip install -r /mnt/skills/private/music-generation/requirements.txt

The requirements.txt includes: music21, midi2audio, pydub, mido, numpy, scipy.

Available SoundFonts

Traditional Pipeline (Orchestral/Acoustic):

• /usr/share/sounds/sf2/FluidR3_GM.sf2 (141MB, General MIDI soundfont for orchestral/classical)
• /usr/share/sounds/sf2/default.sf2 (symlink to best available)

Electronic Pipeline:

• No soundfonts required - uses real-time synthesis for all electronic sounds

Quick Start: Write Custom Compositions

Basic Music Generation Pattern

python
from music21 import stream, note, chord, instrument, tempo, dynamics
from midi2audio import FluidSynth
from pydub import AudioSegment

# 1. Create score and parts
score = stream.Score()
violin_part = stream.Part()
violin_part.insert(0, instrument.Violin())
violin_part.insert(0, tempo.MetronomeMark(number=120))

# 2. Generate notes algorithmically
for measure in range(16):
    violin_part.append(note.Note('E5', quarterLength=1.0))
    violin_part.append(note.Note('G5', quarterLength=1.0))
    violin_part.append(note.Note('A5', quarterLength=2.0))

# 3. Export to MIDI
score.append(violin_part)
midi_path = '/mnt/user-data/outputs/composition.mid'
score.write('midi', fp=midi_path)

# 4. Render with FluidSynth
fs = FluidSynth('/usr/share/sounds/sf2/FluidR3_GM.sf2')
wav_path = '/mnt/user-data/outputs/composition.wav'
fs.midi_to_audio(midi_path, wav_path)

# 5. Convert to MP3
audio = AudioSegment.from_wav(wav_path)
mp3_path = '/mnt/user-data/outputs/composition.mp3'
audio.export(mp3_path, format='mp3', bitrate='192k')

Key Concepts

• Always create downloadable MP3 files (not HTML players)
• All output goes to /mnt/user-data/outputs/
• Use music21.instrument classes: instrument.Violin(), instrument.Violoncello(), instrument.Piano(), instrument.Trumpet(), etc.
• Generate notes programmatically - avoid hardcoded sequences

Choosing the Right Rendering Pipeline

CRITICAL: This skill supports TWO rendering pipelines. You MUST choose based on the musical genre:

Traditional Pipeline (Orchestral, Classical, Acoustic)

Use when creating:

• Orchestral music (violin, cello, trumpet, etc.)
• Classical compositions (Mozart, Beethoven style)
• Piano music, chamber music, symphonies
• Acoustic guitar, brass ensembles
• Any music with traditional/acoustic instruments

How to render:

python
# After composing with music21 and exporting MIDI...
from midi2audio import FluidSynth
from pydub import AudioSegment

fs = FluidSynth('/usr/share/sounds/sf2/FluidR3_GM.sf2')
fs.midi_to_audio(midi_path, wav_path)

audio = AudioSegment.from_wav(wav_path)
audio.export(mp3_path, format='mp3', bitrate='192k')

Electronic Pipeline (House, Techno, EDM, Electronic)

Use when creating:

• House, techno, trance, EDM
• Electronic dance music with synth bass/pads/leads
• DJ beats, club music
• Any music described as "electronic" or "synth-heavy"
• Music referencing DJs like Keinemusik, Black Coffee, etc.

How to render:

python
# After composing with music21, using mido for instruments, and exporting MIDI...
import subprocess

# Use the electronic rendering script
result = subprocess.run([
    'python',
    '/mnt/skills/private/music-generation/scripts/render_electronic.py',
    midi_path,
    mp3_path
], capture_output=True, text=True)

print(result.stdout)
if result.returncode != 0:
    print(f"Error: {result.stderr}")

Why this matters:

• The orchestral soundfont (FluidR3_GM.sf2) sounds terrible for electronic music
• Its "synth" instruments are basic 1990s approximations
• The electronic pipeline uses real-time synthesis for authentic electronic sound
• Synthesizes 808-style kicks, electronic snares, and hi-hats on-the-fly (NO external samples required)
• Bass/pads/leads use subtractive synthesis with filters and ADSR envelopes
• Genre presets (deep_house, techno, trance, ambient) tune synthesis parameters automatically

Drum Synthesis:

The electronic renderer uses real-time drum synthesis (no external samples needed). All drum sounds (kicks, snares, hi-hats, claps) are synthesized on-the-fly with genre-specific parameters.

Example: House Track

python
# 1. Compose with music21 (same as always)
score = stream.Score()
drums = stream.Part()
bass = stream.Part()
pads = stream.Part()
# ... compose your music

# 2. Export MIDI
midi_path = '/mnt/user-data/outputs/deep_house.mid'
score.write('midi', fp=midi_path)

# 3. Fix instruments with mido (INSERT program_change messages)
from mido import MidiFile, Message
mid = MidiFile(midi_path)
for i, track in enumerate(mid.tracks):
    if i == 1:  # Drums
        for msg in track:
            if hasattr(msg, 'channel'):
                msg.channel = 9
    elif i == 2:  # Bass - INSERT program_change
        insert_pos = 0
        for j, msg in enumerate(track):
            if msg.type == 'track_name':
                insert_pos = j + 1
                break
        track.insert(insert_pos, Message('program_change', program=38, time=0))
mid.save(midi_path)

# 4. Render with ELECTRONIC pipeline with deep_house preset!
import subprocess
subprocess.run([
    'python',
    '/mnt/skills/private/music-generation/scripts/render_electronic.py',
    midi_path,
    '/mnt/user-data/outputs/deep_house.mp3',
    '--genre', 'deep_house'
])

Available Genre Presets

The electronic renderer includes pre-tuned synthesis presets with supersaw lead synthesis for thick, professional EDM sounds:

• deep_house: Warm bass with 3-voice leads (120-125 BPM)
• techno: Hard-hitting with 7-voice supersaw leads (125-135 BPM)
• trance: Uplifting with massive 9-voice supersaw leads (130-140 BPM)
• ambient: Soft, atmospheric with 5-voice pads (60-90 BPM)
• acid_house: Squelchy TB-303 bass with 5-voice leads (120-130 BPM)
• default: Balanced 5-voice leads (120-130 BPM)

Supersaw Synthesis (Swedish House Mafia / Progressive House Sound):

The electronic renderer now includes unison voice synthesis for fat, buzzy leads:

• Multiple detuned oscillators: 3-9 sawtooth waves per note (genre-dependent)
• Aggressive detuning: 6-15 cents spread creates buzzy chorus effect
• Enhanced saturation: 2.5x distortion for punch and aggression
• Phase spreading: Creates wide stereo image

How It Works:

• House: 3 voices, ±8 cents (subtle, warm)
• Techno: 7 voices, ±12 cents (aggressive, punchy)
• Trance: 9 voices, ±15 cents (massive, soaring)
• Acid house: 5 voices, ±12 cents (squelchy, aggressive)

This replicates the classic supersaw sound from Swedish House Mafia, Avicii, and modern EDM productions.

Each preset tunes:

• Drum synthesis: kick pitch/decay/punch, snare tone/snap, hat brightness/metallic
• Bass synthesis: waveform, filter cutoff/resonance, ADSR envelope
• Pad synthesis: attack/release times, detune amount, brightness
• Lead synthesis: brightness, envelope, portamento
• Volume balance: intelligent mix levels per instrument with frequency-aware compensation
• Velocity curves: exponential, linear, or logarithmic response to MIDI velocity

Intelligent Volume Management

The electronic renderer uses frequency-aware volume balancing to prevent any instrument from overpowering the mix:

How it works:

• Bass frequencies (<100Hz): Automatically reduced by -4 to -6dB (sub-bass has high perceived energy)
• Mid frequencies (200-800Hz): Balanced naturally
• High frequencies (>800Hz): Slightly boosted for clarity (+1 to +1.5dB)
• Genre-specific balance: Each preset has optimized levels (e.g., House bass gets -3dB)
• Velocity curves: MIDI velocity maps intelligently (not just linear)
• Auto-limiting: Final mix is limited to -1dB to prevent clipping

Why this matters:

• House bass (A1, E2) at 55-82Hz naturally has more power - now automatically compensated
• Prevents "bass overpowering everything" issues
• Maintains balanced mix across all genres
• No manual volume tweaking needed

To see all available presets:

bash
python /mnt/skills/private/music-generation/scripts/render_electronic.py --list-genres

Customizing Synthesis Parameters

For advanced control, you can create custom preset JSON files:

json
{
  "drums": {
    "kick": {"pitch": 52.0, "decay": 0.6, "punch": 0.9},
    "snare": {"tone_mix": 0.25, "snap": 0.8}
  },
  "bass": {
    "waveform": "sawtooth",
    "cutoff": 180,
    "resonance": 0.7
  },
  "pad": {
    "attack": 1.0,
    "brightness": 0.35
  }
}

Then use with --preset:

bash
python render_electronic.py track.mid output.mp3 --preset my_preset.json

Advanced Workflow: Learn from Existing MIDI

For classical pieces or complex compositions, you can:

1. Extract Structure from ANY MIDI File

bash
python /mnt/skills/private/music-generation/scripts/midi_inventory.py \
    path/to/mozart.mid \
    /mnt/user-data/outputs/mozart_structure.json

This extracts:

• Tempo, key signature, time signature
• Track information and instruments
• Complete note sequences with timing
• Musical structure

2. Modify the JSON Structure

python
import json

# Load extracted structure
with open('/mnt/user-data/outputs/mozart_structure.json', 'r') as f:
    structure = json.load(f)

# Modify instruments, notes, timing, etc.
structure['tracks']['track-0']['instrument'] = 'violin'  # Change piano to violin!

# Save modified structure
with open('/mnt/user-data/outputs/mozart_violin.json', 'w') as f:
    json.dump(structure, f)

3. Render Modified Structure to MP3

bash
python /mnt/skills/private/music-generation/scripts/midi_render.py \
    /mnt/user-data/outputs/mozart_violin.json \
    /mnt/user-data/outputs/mozart_violin.mp3

This workflow lets you "recreate" any classical piece with different instruments!

Available Scripts

All scripts are located in /mnt/skills/private/music-generation/scripts/:

Main Workflow Scripts:

• render_electronic.py - Electronic music renderer with real-time synthesis (drums, bass, pads, leads)
• midi_inventory.py - Extract complete structure from ANY MIDI file to JSON format
• midi_render.py - Render JSON music structure to MP3 using FluidSynth
• midi_transform.py - Generic MIDI transformations (transpose, tempo change, instrument swap)
• audio_validate.py - Validate audio file quality and format

Synthesis Engine (used by render_electronic.py):

• drum_synthesizer.py - Synthesizes kicks, snares, hi-hats, claps on-the-fly
• melodic_synthesizer.py - Synthesizes bass, pads, and lead sounds using subtractive synthesis
• synthesis_presets.py - Genre presets (deep_house, techno, trance, ambient, etc.)
• midi_utils.py - MIDI parsing utilities for extracting events and metadata
• __init__.py - Python package marker (allows importing scripts as modules)

Utility Scripts:

Music Theory Reference

Complete General MIDI Instrument Map (Programs 0-127)

CRITICAL: music21 has limited instrument support. For most sounds (especially electronic), you MUST use mido to set program numbers after export.

python
# Piano (0-7)
0: "Acoustic Grand Piano"
1: "Bright Acoustic Piano"
2: "Electric Grand Piano"
3: "Honky-tonk Piano"
4: "Electric Piano 1"
5: "Electric Piano 2"
6: "Harpsichord"
7: "Clavinet"

# Chromatic Percussion (8-15)
8: "Celesta"
9: "Glockenspiel"
10: "Music Box"
11: "Vibraphone"
12: "Marimba"
13: "Xylophone"
14: "Tubular Bells"
15: "Dulcimer"

# Organ (16-23)
16: "Drawbar Organ"
17: "Percussive Organ"
18: "Rock Organ"
19: "Church Organ"
20: "Reed Organ"
21: "Accordion"
22: "Harmonica"
23: "Tango Accordion"

# Guitar (24-31)
24: "Acoustic Guitar (nylon)"
25: "Acoustic Guitar (steel)"
26: "Electric Guitar (jazz)"
27: "Electric Guitar (clean)"
28: "Electric Guitar (muted)"
29: "Overdriven Guitar"
30: "Distortion Guitar"
31: "Guitar Harmonics"

# Bass (32-39)
32: "Acoustic Bass"
33: "Electric Bass (finger)"
34: "Electric Bass (pick)"
35: "Fretless Bass"
36: "Slap Bass 1"
37: "Slap Bass 2"
38: "Synth Bass 1"
39: "Synth Bass 2"

# Strings (40-47)
40: "Violin"
41: "Viola"
42: "Cello"
43: "Contrabass"
44: "Tremolo Strings"
45: "Pizzicato Strings"
46: "Orchestral Harp"
47: "Timpani"

# Ensemble (48-55)
48: "String Ensemble 1"
49: "String Ensemble 2"
50: "Synth Strings 1"
51: "Synth Strings 2"
52: "Choir Aahs"
53: "Voice Oohs"
54: "Synth Voice"
55: "Orchestra Hit"

# Brass (56-63)
56: "Trumpet"
57: "Trombone"
58: "Tuba"
59: "Muted Trumpet"
60: "French Horn"
61: "Brass Section"
62: "Synth Brass 1"
63: "Synth Brass 2"

# Reed (64-71)
64: "Soprano Sax"
65: "Alto Sax"
66: "Tenor Sax"
67: "Baritone Sax"
68: "Oboe"
69: "English Horn"
70: "Bassoon"
71: "Clarinet"

# Pipe (72-79)
72: "Piccolo"
73: "Flute"
74: "Recorder"
75: "Pan Flute"
76: "Blown Bottle"
77: "Shakuhachi"
78: "Whistle"
79: "Ocarina"

# Synth Lead (80-87)
80: "Lead 1 (square)"
81: "Lead 2 (sawtooth)"
82: "Lead 3 (calliope)"
83: "Lead 4 (chiff)"
84: "Lead 5 (charang)"
85: "Lead 6 (voice)"
86: "Lead 7 (fifths)"
87: "Lead 8 (bass + lead)"

# Synth Pad (88-95)
88: "Pad 1 (new age)"
89: "Pad 2 (warm)"
90: "Pad 3 (polysynth)"
91: "Pad 4 (choir)"
92: "Pad 5 (bowed)"
93: "Pad 6 (metallic)"
94: "Pad 7 (halo)"
95: "Pad 8 (sweep)"

# Synth Effects (96-103)
96: "FX 1 (rain)"
97: "FX 2 (soundtrack)"
98: "FX 3 (crystal)"
99: "FX 4 (atmosphere)"
100: "FX 5 (brightness)"
101: "FX 6 (goblins)"
102: "FX 7 (echoes)"
103: "FX 8 (sci-fi)"

# Ethnic (104-111)
104: "Sitar"
105: "Banjo"
106: "Shamisen"
107: "Koto"
108: "Kalimba"
109: "Bag pipe"
110: "Fiddle"
111: "Shanai"

# Percussive (112-119)
112: "Tinkle Bell"
113: "Agogo"
114: "Steel Drums"
115: "Woodblock"
116: "Taiko Drum"
117: "Melodic Tom"
118: "Synth Drum"
119: "Reverse Cymbal"

# Sound Effects (120-127)
120: "Guitar Fret Noise"
121: "Breath Noise"
122: "Seashore"
123: "Bird Tweet"
124: "Telephone Ring"
125: "Helicopter"
126: "Applause"
127: "Gunshot"

Complete Drum Map (MIDI Channel 10, Notes 35-81)

Drums use note numbers for different sounds, NOT pitch. Must be on channel 10 (9 in 0-indexed).

python
# Bass Drums
35: "Acoustic Bass Drum"
36: "Bass Drum 1"  # Most common kick

# Snares
38: "Acoustic Snare"  # Standard snare
40: "Electric Snare"

# Toms
41: "Low Floor Tom"
43: "High Floor Tom"
45: "Low Tom"
47: "Low-Mid Tom"
48: "Hi-Mid Tom"
50: "High Tom"

# Hi-Hats
42: "Closed Hi-Hat"  # Most used
44: "Pedal Hi-Hat"
46: "Open Hi-Hat"

# Cymbals
49: "Crash Cymbal 1"
51: "Ride Cymbal 1"
52: "Chinese Cymbal"
53: "Ride Bell"
55: "Splash Cymbal"
57: "Crash Cymbal 2"
59: "Ride Cymbal 2"

# Percussion
37: "Side Stick"
39: "Hand Clap"
54: "Tambourine"
56: "Cowbell"
58: "Vibraslap"
60: "Hi Bongo"
61: "Low Bongo"
62: "Mute Hi Conga"
63: "Open Hi Conga"
64: "Low Conga"
65: "High Timbale"
66: "Low Timbale"
67: "High Agogo"
68: "Low Agogo"
69: "Cabasa"
70: "Maracas"
71: "Short Whistle"
72: "Long Whistle"
73: "Short Guiro"
74: "Long Guiro"
75: "Claves"
76: "Hi Wood Block"
77: "Low Wood Block"
78: "Mute Cuica"
79: "Open Cuica"
80: "Mute Triangle"
81: "Open Triangle"

How to Use Any Instrument (mido workflow)

music21 has built-in classes for orchestral instruments (Violin, Piano, Trumpet, etc.) but NO support for synths, electronic instruments, or many others. To use any GM instrument:

CRITICAL RULE: When you create a stream.Part() WITHOUT assigning a music21 instrument class, music21 WILL NOT create program_change messages in the MIDI file. You MUST use mido to INSERT these messages manually. Simply trying to modify them with if msg.type == 'program_change': msg.program = X will fail silently because no such messages exist!

Helper Function for Setting Instruments:

python
from mido import Message

def set_track_instrument(track, program):
    """Insert a program_change message at the beginning of a MIDI track."""
    insert_pos = 0
    for j, msg in enumerate(track):
        if msg.type == 'track_name':
            insert_pos = j + 1
            break
    track.insert(insert_pos, Message('program_change', program=program, time=0))

# Usage after loading MIDI with mido:
# set_track_instrument(mid.tracks[2], 33)  # Set track 2 to Electric Bass

Step 1: Compose with music21 (use placeholder or skip instrument)

python
from music21 import stream, note, chord, tempo

score = stream.Score()

# Create parts - don't worry about instrument assignment yet
synth_lead = stream.Part()
synth_pad = stream.Part()
bass = stream.Part()

# Add your notes/chords
synth_lead.append(note.Note('E5', quarterLength=1.0))
# ... compose your music

score.append(synth_lead)
score.append(synth_pad)
score.append(bass)

# Export to MIDI
midi_path = '/mnt/user-data/outputs/track.mid'
score.write('midi', fp=midi_path)

Step 2: Assign correct instruments with mido

python
from mido import MidiFile, Message

mid = MidiFile(midi_path)

# Track 0 is tempo/metadata, actual parts start at track 1
# CRITICAL: You must INSERT program_change messages, not just modify existing ones!
# music21 doesn't create program_change messages if you don't assign instruments

for i, track in enumerate(mid.tracks):
    if i == 1:  # First part (synth_lead)
        # Insert program_change at beginning of track (after track name if present)
        insert_pos = 0
        for j, msg in enumerate(track):
            if msg.type == 'track_name':
                insert_pos = j + 1
                break
        track.insert(insert_pos, Message('program_change', program=80, time=0))

    elif i == 2:  # Second part (synth_pad)
        insert_pos = 0
        for j, msg in enumerate(track):
            if msg.type == 'track_name':
                insert_pos = j + 1
                break
        track.insert(insert_pos, Message('program_change', program=88, time=0))

    elif i == 3:  # Third part (bass)
        insert_pos = 0
        for j, msg in enumerate(track):
            if msg.type == 'track_name':
                insert_pos = j + 1
                break
        track.insert(insert_pos, Message('program_change', program=38, time=0))

mid.save(midi_path)

Step 3: For drums, ALSO set channel to 9 (channel 10)

python
# If track is drums, set ALL messages to channel 9
for i, track in enumerate(mid.tracks):
    if i == 1:  # This is the drum track
        for msg in track:
            if hasattr(msg, 'channel'):
                msg.channel = 9  # Channel 10 in 1-indexed

Step 4: Render to audio

python
from midi2audio import FluidSynth
from pydub import AudioSegment

fs = FluidSynth('/usr/share/sounds/sf2/FluidR3_GM.sf2')
wav_path = '/mnt/user-data/outputs/track.wav'
fs.midi_to_audio(midi_path, wav_path)

audio = AudioSegment.from_wav(wav_path)
mp3_path = '/mnt/user-data/outputs/track.mp3'
audio.export(mp3_path, format='mp3', bitrate='192k')

Common Chord Progressions & Styles

python
# Standard Progressions (Roman numerals)
"pop": ["I", "V", "vi", "IV"]           # C-G-Am-F (Journey, Adele)
"epic": ["i", "VI", "III", "VII"]       # Am-F-C-G (Epic trailer music)
"sad": ["i", "VI", "iv", "V"]           # Am-F-Dm-E (Melancholic)
"jazz": ["ii", "V", "I", "vi"]          # Dm-G-C-Am (Jazz standard)
"classical": ["I", "IV", "V", "I"]      # C-F-G-C (Classical cadence)
"blues": ["I", "I", "I", "I", "IV", "IV", "I", "I", "V", "IV", "I", "I"]  # 12-bar blues
"house": ["i", "VI", "III", "VII"]      # Minor house progression
"reggae": ["I", "V", "vi", "IV"]        # Offbeat rhythm style
"country": ["I", "IV", "V", "I"]        # Simple and direct
"rock": ["I", "bVII", "IV", "I"]        # Power chord style
"r&b": ["I", "V", "vi", "iii", "IV", "I", "IV", "V"]  # Complex R&B

# Genre-Specific Characteristics
STYLES = {
    "house": {
        "bpm": 120-128,
        "time_signature": "4/4",
        "drum_pattern": "4-on-floor kick, offbeat hats",
        "bass": "Synth bass with groove",
        "common_instruments": [38, 80, 88, 4]  # Synth bass, lead, pad, e-piano
    },
    "jazz": {
        "bpm": 100-180,
        "time_signature": "4/4 or 3/4",
        "chords": "Extended (7th, 9th, 11th, 13th)",
        "common_instruments": [0, 32, 64, 56, 73]  # Piano, bass, sax, trumpet, drums
    },
    "orchestral": {
        "bpm": 60-140,
        "sections": ["strings", "woodwinds", "brass", "percussion"],
        "common_instruments": [40, 41, 42, 56, 73, 47]  # Violin, viola, cello, trumpet, flute, timpani
    },
    "rock": {
        "bpm": 100-140,
        "time_signature": "4/4",
        "guitars": "Distorted (30) or clean (27)",
        "common_instruments": [30, 33, 0, 128]  # Distortion guitar, bass, piano, drums
    },
    "ambient": {
        "bpm": 60-90,
        "characteristics": "Long sustained notes, atmospheric pads",
        "common_instruments": [88, 89, 90, 91, 52]  # Various pads, choir
    },
    "trap": {
        "bpm": 130-170,
        "drums": "Tight snare rolls, 808 bass kicks",
        "hi_hats": "Fast hi-hat patterns (1/16 or 1/32 notes)",
        "common_instruments": [38, 128]  # Synth bass, drums
    }
}

music21 Instrument Classes

python
from music21 import instrument

# Strings
instrument.Violin()
instrument.Viola()
instrument.Violoncello()  # Note: NOT Cello()
instrument.Contrabass()
instrument.Harp()

# Piano
instrument.Piano()
instrument.Harpsichord()

# Brass
instrument.Trumpet()
instrument.Trombone()
instrument.Tuba()
instrument.Horn()  # French horn

# Woodwinds
instrument.Flute()
instrument.Clarinet()
instrument.Oboe()
instrument.Bassoon()
instrument.SopranoSaxophone()
instrument.AltoSaxophone()
instrument.TenorSaxophone()  # Most common for jazz
instrument.BaritoneSaxophone()

# Other
instrument.AcousticGuitar()
instrument.ElectricGuitar()
instrument.Bass()
instrument.Timpani()

# CRITICAL: music21 has LIMITED support for electronic instruments and drums
# For synths, drums, and electronic sounds, you MUST:
# 1. Create a Part without an instrument (or use a placeholder like Piano())
# 2. Use mido library to INSERT program_change messages after export
# 3. Set drums to MIDI channel 10 (channel 9 in 0-indexed) or they won't sound like drums
#
# Common mistakes:
# - instrument.Cello() doesn't exist - use Violoncello()
# - instrument.FrenchHorn() doesn't exist - use Horn()
# - Setting part.partName doesn't change the sound - you must set MIDI program with mido
# - Drums on channel 0 will play as pitched notes, not drum sounds

Note Durations (Quarter Note = 1.0)

• Whole note: 4.0
• Half note: 2.0
• Quarter note: 1.0
• Eighth note: 0.5
• Sixteenth note: 0.25
• Dotted quarter: 1.5
• Triplet quarter: 0.667

mido Quick Reference

For electronic music and drums, use mido to set MIDI programs after music21 export:

python
from mido import MidiFile, Message

mid = MidiFile(midi_path)

# Insert program_change message
for i, track in enumerate(mid.tracks):
    if i == 1:  # Your track (tracks start at 1, not 0)
        insert_pos = 0
        for j, msg in enumerate(track):
            if msg.type == 'track_name':
                insert_pos = j + 1
                break
        track.insert(insert_pos, Message('program_change', program=38, time=0))

# For drums: Set channel to 9 (channel 10 in 1-indexed)
for i, track in enumerate(mid.tracks):
    if i == 1:  # Drum track
        for msg in track:
            if hasattr(msg, 'channel'):
                msg.channel = 9

mid.save(midi_path)

Common MIDI Programs:

• 38: Synth Bass 1
• 80: Square Lead
• 81: Sawtooth Lead
• 88: Pad 1 (New Age)
• 25: Acoustic Guitar (Steel) - loud, cuts through
• 33: Acoustic Bass

Common Techniques

Drum Programming (4-on-floor house beat)

CRITICAL: music21's .append() adds notes sequentially (one after another), not simultaneously. For layered drums where kicks, snares, and hats play at the same time, you MUST use .insert(offset, note) with explicit timing.

⚠️ ALWAYS USE .insert() FOR ALL TRACKS:

Since layering is needed for nearly all good music composition, you should ALWAYS use .insert(offset, note) for ALL tracks - drums, bass, guitar, pads, everything. This prevents timing bugs and ensures proper synchronization.

NEVER mix .insert() and .append() - If you use .insert() for drums and .append() for other instruments, music21 will miscalculate track lengths and create tracks that are 5-10× longer than intended (8 minutes instead of 1.5 minutes), with only the first 20-25% containing actual sound.

The .append() method should only be used in rare cases where you have a single melodic line with no other instruments.

python
# WRONG: This plays kick, then 32 hats, then snare pattern (not layered!)
# for beat in range(16):
#     drums.append(note.Note(36, quarterLength=1.0))  # Kicks play first
# for eighth in range(32):
#     drums.append(note.Note(42, quarterLength=0.5))  # Hats play AFTER all kicks
# # Result: Timing is completely wrong!

# CORRECT: Use .insert() with explicit offsets for simultaneous layering
bars = 32
beats_per_bar = 4
total_beats = bars * beats_per_bar

# Layer 1: Four-on-the-floor kicks (every beat)
for beat in range(total_beats):
    offset = float(beat)  # Beat 0, 1, 2, 3, 4, 5, ...
    drums.insert(offset, note.Note(36, quarterLength=1.0))

# Layer 2: Snare on beats 2 and 4 of each bar
for bar in range(bars):
    # Snare on beat 2 (second beat of bar)
    offset = float(bar * beats_per_bar + 1)
    drums.insert(offset, note.Note(38, quarterLength=1.0))

    # Snare on beat 4 (fourth beat of bar)
    offset = float(bar * beats_per_bar + 3)
    drums.insert(offset, note.Note(38, quarterLength=1.0))

# Layer 3: Hi-hats on eighth notes (every 0.5 beats) - creates groove
for bar in range(bars):
    for eighth in range(8):  # 8 eighth notes per bar
        offset = float(bar * beats_per_bar) + (eighth * 0.5)

        if eighth % 2 == 0:
            # Closed hat on even eighths (on the beat)
            drums.insert(offset, note.Note(42, quarterLength=0.5))
        else:
            # Open hat on odd eighths (offbeat) - signature house groove
            drums.insert(offset, note.Note(46, quarterLength=0.5))

# Result: Properly layered four-on-the-floor with offbeat open hats
# Bar 0: Kicks at 0.0, 1.0, 2.0, 3.0
#        Snares at 1.0, 3.0 (on top of kicks)
#        Hats at 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 (layered throughout)

Reggae Specific Guidelines

CRITICAL: Reggae has a unique rhythmic identity that requires precise drum patterns, offbeat accents, and heavy bass. If you don't follow these rules, it won't sound like reggae.

Drum Rules (Non-Negotiable):

• "One Drop" pattern: Kick drum on beat 3 ONLY (not beat 1), creating the signature reggae "drop"
• Snare/Rimshot: Beats 2 and 4 (or just beat 3 with the kick)
• Hi-hats: OFFBEAT eighth notes only (never on the beat), creating the "skank" rhythm
• Cross-stick (note 37): Optional on beats 2 and 4 for classic sound
• NO four-on-floor kicks - this is house/electronic, not reggae

python
# CORRECT Reggae "One Drop" Drum Pattern
bars = 32
beats_per_bar = 4

for bar in range(bars):
    for beat in range(beats_per_bar):
        offset = float(bar * beats_per_bar + beat)

        # Kick ONLY on beat 3 (the "drop")
        if beat == 2:  # Beat 3 in 0-indexed (0, 1, 2, 3)
            drums_part.insert(offset, note.Note(36, quarterLength=1.0))

        # Snare on beats 2 and 4
        if beat == 1 or beat == 3:
            drums_part.insert(offset, note.Note(38, quarterLength=1.0))

    # OFFBEAT hi-hats (the "skank") - CRITICAL for reggae feel
    for eighth in range(8):
        offset = float(bar * beats_per_bar) + (eighth * 0.5)
        # ONLY odd eighths (offbeat) - never on the beat
        if eighth % 2 == 1:  # 0.5, 1.5, 2.5, 3.5 (offbeat)
            drums_part.insert(offset, note.Note(42, quarterLength=0.5))

# WRONG - Four-on-floor (this is house, not reggae!)
# for beat in range(total_beats):
#     drums_part.insert(float(beat), note.Note(36, quarterLength=1.0))  # ❌ Kick on every beat

Bass Rules (Non-Negotiable):

• Heavy and prominent - Bass is the lead instrument in reggae
• Octave 1-2 (A1, C2, E2, F1, G1) - not too low, not too high
• Syncopated rhythm - plays between beats, not just on downbeats
• Walking patterns - moves between root, third, fifth of chords
• Quarter to half notes (1.0-2.0 quarterLength) - NOT whole notes like House

python
# CORRECT Reggae Bass (Am-D-F-G progression, 8-bar pattern)
# This pattern has movement and syncopation - it "walks"
bass_pattern = [
    # Bar 1-2: Am (root A)
    ('A1', 1.0), ('A1', 0.5), ('C2', 0.5), ('A1', 2.0),  # Bar 1
    ('A1', 1.0), ('E2', 1.0), ('A1', 2.0),                # Bar 2

    # Bar 3-4: D (root D)
    ('D2', 1.0), ('D2', 0.5), ('F2', 0.5), ('D2', 2.0),  # Bar 3
    ('D2', 1.0), ('A1', 1.0), ('D2', 2.0),                # Bar 4

    # Bar 5-6: F (root F)
    ('F1', 1.0), ('F1', 0.5), ('A1', 0.5), ('F1', 2.0),  # Bar 5
    ('F1', 1.0), ('C2', 1.0), ('F1', 2.0),                # Bar 6

    # Bar 7-8: G (root G, with E for resolution)
    ('G1', 1.0), ('G1', 0.5), ('B1', 0.5), ('E2', 2.0),  # Bar 7
    ('G1', 1.0), ('D2', 1.0), ('E2', 2.0),                # Bar 8
]

# Use .insert() to place bass notes at explicit offsets (synchronizes with drums)
offset = 0.0
for repetition in range(bars // 8):
    for pitch, duration in bass_pattern:
        bass_part.insert(offset, note.Note(pitch, quarterLength=duration))
        offset += duration

# WRONG - Using .append() will cause 8-minute tracks when mixed with .insert() drums
# for pitch, duration in bass_pattern * (bars // 8):
#     bass_part.append(note.Note(pitch, quarterLength=duration))  # ❌ Causes timing bug!

Guitar "Skank" Rules (Non-Negotiable):

• OFFBEAT chords only - plays on upbeats (the "and" of beats), never downbeats
• CRITICAL: Sufficient duration - Minimum 0.35-0.4 quarterLength (NOT 0.25) to be audible in mix
• Mid-register voicings - Octaves 3-4 (A3, C4, E4)
• Muted/percussive - In real reggae, these are muted strums creating rhythm

⚠️ CRITICAL NOTE DURATION WARNING:

At 0.25 quarterLength, guitar will be completely inaudible in the mix:

• At 82 BPM: (60 / 82) × 0.25 = 0.183 seconds (183 milliseconds)
• Human perceptual threshold: ~200-300ms needed to register in dense mix
• Organ plays at 0.5 (366ms) - TWICE as long

Use 0.4 quarterLength minimum:

• At 82 BPM: (60 / 82) × 0.4 = 0.293 seconds (293 milliseconds)
• Crosses perceptual threshold while maintaining staccato feel
• Adjust rest to 0.1 to maintain 1.0 beat total per skank cycle

python
# CORRECT Reggae Guitar "Skank" (offbeat chords with AUDIBLE duration)
guitar_chords = [
    ['A3', 'C4', 'E4'],    # Am
    ['A3', 'C4', 'E4'],    # Am (repeat for 2 bars)
    ['D3', 'F#3', 'A3'],   # D
    ['D3', 'F#3', 'A3'],   # D (repeat for 2 bars)
    ['F3', 'A3', 'C4'],    # F
    ['F3', 'A3', 'C4'],    # F (repeat for 2 bars)
    ['G3', 'B3', 'D4'],    # G
    ['G3', 'B3', 'D4'],    # G (repeat for 2 bars)
]

# Use .insert() to place guitar at explicit offsets (synchronizes with drums/bass)
offset = 0.0
for repetition in range(bars // 8):
    for chord_notes in guitar_chords:
        # Each bar: 4 offbeat skanks
        for beat in range(4):
            # REST on the beat (downbeat)
            guitar_part.insert(offset, note.Rest(quarterLength=0.5))
            offset += 0.5
            # CHORD on the offbeat (upbeat) - 0.4 duration for audibility
            guitar_part.insert(offset, chord.Chord(chord_notes, quarterLength=0.4))
            offset += 0.4
            # SHORT REST after chord (creates staccato effect)
            guitar_part.insert(offset, note.Rest(quarterLength=0.1))
            offset += 0.1

# WRONG - Using .append() causes 8-minute tracks when mixed with .insert() drums
# guitar_part.append(chord.Chord(chord_notes, quarterLength=0.4))  # ❌ Causes timing bug!

# WRONG - Duration too short (will be inaudible!)
# guitar_part.insert(offset, chord.Chord(chord_notes, quarterLength=0.25))  # ❌ Only 183ms @ 82 BPM

Organ "Bubble" Rules:

• Alternating on-and-off pattern - Creates rhythmic "bubbling" effect
• Higher register (octaves 4-5) - Sits above guitar
• Plays same chords as guitar but different rhythm
• Shorter duration (0.5 quarterLength) with rests between

python
# CORRECT Reggae Organ "Bubble"
organ_chords = [
    ['A4', 'C5', 'E5'],    # Am (high register)
    ['A4', 'C5', 'E5'],
    ['D4', 'F#4', 'A4'],   # D
    ['D4', 'F#4', 'A4'],
    ['F4', 'A4', 'C5'],    # F
    ['F4', 'A4', 'C5'],
    ['G4', 'B4', 'D5'],    # G
    ['G4', 'B4', 'D5'],
]

# Use .insert() to place organ at explicit offsets (synchronizes with drums/bass/guitar)
offset = 0.0
for repetition in range(bars // 8):
    for organ_chord in organ_chords:
        # Each bar: bubble pattern (chord, rest, chord, rest)
        for _ in range(2):  # Twice per bar
            organ_part.insert(offset, chord.Chord(organ_chord, quarterLength=0.5))
            offset += 0.5
            organ_part.insert(offset, note.Rest(quarterLength=0.5))
            offset += 0.5
            organ_part.insert(offset, chord.Chord(organ_chord, quarterLength=0.5))
            offset += 0.5
            organ_part.insert(offset, note.Rest(quarterLength=0.5))
            offset += 0.5

# WRONG - Using .append() causes 8-minute tracks when mixed with .insert() drums
# organ_part.append(chord.Chord(organ_chord, quarterLength=0.5))  # ❌ Causes timing bug!

Reggae Instruments (MIDI Programs):

• Drums: Channel 9 (MIDI channel 10) - ALWAYS required
• Bass: Program 33 (Electric Bass - finger) or 34 (Electric Bass - pick)
• Guitar:
• PRIMARY: Program 25 (Acoustic Guitar - steel) - Bright, percussive, cuts through mix
• Alternative: Program 28 (Electric Guitar - muted) - Percussive skank sound
• ⚠️ AVOID: Program 27 (Electric Guitar - clean) - Recorded 12-15dB quieter in FluidR3_GM, will be inaudible even at velocity 95
• Organ: Program 16 (Drawbar Organ) or 17 (Percussive Organ)

Setting Instruments with mido (CRITICAL):

Since reggae Parts don't use music21 instrument classes, you MUST use mido to INSERT program_change messages:

python
from mido import MidiFile, Message

# After score.write('midi', fp=midi_path)
mid = MidiFile(midi_path)

for i, track in enumerate(mid.tracks):
    if i == 1:  # Drums track
        for msg in track:
            if hasattr(msg, 'channel'):
                msg.channel = 9  # Drums on channel 9
    elif i == 2:  # Bass track
        # INSERT program_change message (don't try to modify - it doesn't exist!)
        insert_pos = 0
        for j, msg in enumerate(track):
            if msg.type == 'track_name':
                insert_pos = j + 1
                break
        track.insert(insert_pos, Message('program_change', program=33, time=0))
    elif i == 3:  # Guitar track
        insert_pos = 0
        for j, msg in enumerate(track):
            if msg.type == 'track_name':
                insert_pos = j + 1
                break
        track.insert(insert_pos, Message('program_change', program=25, time=0))  # Acoustic steel - bright and audible
    elif i == 4:  # Organ track
        insert_pos = 0
        for j, msg in enumerate(track):
            if msg.type == 'track_name':
                insert_pos = j + 1
                break
        track.insert(insert_pos, Message('program_change', program=16, time=0))

mid.save(midi_path)

Mixing and Balance (CRITICAL - Guitar Will Be Inaudible Without This!):

Setting the correct instrument programs and velocities is NOT enough. In reggae, the guitar will still be completely inaudible if you don't address THREE issues:

1. Soundfont level: Program 27 (Electric Guitar - clean) recorded 12-15dB quieter than program 16 (Drawbar Organ) in FluidR3_GM
2. Note duration: 0.25 quarterLength = 183ms @ 82 BPM (below perceptual threshold)
3. Velocity difference: Need 40+ point separation

Complete Solution:

python
def set_track_velocity(track, velocity):
    """Set velocity for all note_on messages in a track."""
    for msg in track:
        if msg.type == 'note_on' and msg.velocity > 0:
            msg.velocity = velocity

# After setting instruments, BEFORE saving
for i, track in enumerate(mid.tracks):
    if i == 1:  # Drums
        set_track_velocity(track, 70)
    elif i == 2:  # Bass - prominent in reggae
        set_track_velocity(track, 80)
    elif i == 3:  # Guitar - RHYTHM INSTRUMENT, needs to cut through
        # Use program 25 (steel acoustic) instead of 27 (too quiet)
        # Use 0.4 quarterLength instead of 0.25 (too short)
        set_track_velocity(track, 95)  # LOUD - this is critical!
    elif i == 4:  # Organ - BACKGROUND atmosphere
        set_track_velocity(track, 55)  # QUIET - don't overpower guitar

mid.save(midi_path)

Why this THREE-PART solution works:

• Program 25 (Acoustic Guitar - steel): Recorded 8-10dB louder than program 27, bright harmonics, percussive attack
• Duration 0.4 (293ms): Crosses perceptual threshold vs 0.25 (183ms) which is too short
• Velocity 95 vs 55: 40-point difference creates clear separation
• Combined effect: Guitar now has 3× more presence (program × duration × velocity)

Tempo: 70-90 BPM (classic roots reggae: 80-85 BPM, modern: 85-90 BPM)

Common Mistakes:

• Creating drums_part but calling drums.insert() - use correct variable name
• Trying to MODIFY program_change messages that don't exist - must INSERT them
• Not setting drums to channel 9 - drums will sound like melody notes
• CRITICAL: Using program 27 (too quiet) instead of program 25
• CRITICAL: Using 0.25 quarterLength (too short) instead of 0.4
• CRITICAL: Not setting velocities - guitar will be completely inaudible, organ will dominate

House Specific Guidelines

CRITICAL: House requires extreme repetition and minimal variation to create the hypnotic, groovy feel. Standard composition rules don't apply.

Bass Rules (Non-Negotiable):

• ONE NOTE held for 8-16 bars minimum (32.0-64.0 quarterLength)
• Octave 1-2 RANGE (A1, C2, E2, F1, G1) - the actual bass guitar range (55-110 Hz)
• NEVER use octave 0 (A0, F0, G0, etc.) - these are 20-30 Hz sub-sonic frequencies inaudible on 99% of playback systems (laptop speakers, headphones, even many studio monitors can't reproduce them)
• Whole notes or longer (4.0+ quarterLength minimum, prefer 32.0+)
• Simple patterns: Root for 8 bars → Fifth for 8 bars → repeat
• NO octave jumps, NO busy basslines, NO quarter notes

python
# CORRECT House Bass (audible on all playback systems)
bass_pattern = [
    ('A1', 32.0),  # A for 8 bars - 55 Hz (bass guitar's lowest note)
    ('E2', 32.0),  # E for 8 bars - 82 Hz (bass guitar's open E string)
    ('F1', 32.0),  # F for 8 bars - 43.7 Hz
    ('C2', 32.0),  # C for 8 bars - 65.4 Hz
]
for pitch, duration in bass_pattern:
    bass_part.append(note.Note(pitch, quarterLength=duration))

# WRONG - Octave 0 is inaudible on most systems!
bass_notes = ['A0', 'F0', 'C1', 'G0']  # ❌ 20-35 Hz - below hearing/speaker range!
for bar in range(8):
    bass_part.append(note.Note(bass_notes[bar % 4], quarterLength=32.0))  # ❌ Inaudible!

# ALSO WRONG - Too busy, octave jumps
bass_notes = ['A1', 'A2', 'C2', 'F1']  # ❌ Octave jumps
for bar in range(32):
    bass_part.append(note.Note(bass_notes[bar % 4], quarterLength=1.0))  # ❌ Too short!

Pad Rules:

• ONE CHORD held for 8-16 bars (32.0-64.0 quarterLength)
• Mid-range octaves (2-4): A2, C3, E3 voicings
• Long attack/release for smooth transitions
• Change chords rarely (every 8-16 bars, not every 4 bars)

python
# CORRECT House Pads
pad_progression = [
    (['A2', 'C3', 'E3'], 64.0),  # Am for 16 bars
    (['F2', 'A2', 'C3'], 64.0),  # F for 16 bars
]
for chord_notes, duration in pad_progression:
    pad_part.append(chord.Chord(chord_notes, quarterLength=duration))

Lead Rules:

• Sparse - only play every 4-8 bars, lots of silence
• Long notes (4.0-16.0 quarterLength)
• Enter late (bar 16+, not immediately)
• Mid octaves (A4, C5, E5 max)

python
# CORRECT House Lead (enters bar 16)
lead_pattern = [
    ('A4', 8.0),   # 2 bars
    ('C5', 8.0),   # 2 bars
    ('E5', 16.0),  # 4 bars
]

Core Principle: If it feels repetitive, you're doing it right. House = hypnotic loop repeated for minutes with minimal changes.

Mixing and Balance:

In House, the bass is the star. But if you don't control velocities, the pads and leads will overpower everything:

python
def set_track_velocity(track, velocity):
    """Set velocity for all note_on messages in a track."""
    for msg in track:
        if msg.type == 'note_on' and msg.velocity > 0:
            msg.velocity = velocity

# After setting instruments with mido
for i, track in enumerate(mid.tracks):
    if i == 1:  # Drums
        set_track_velocity(track, 90)  # Driving rhythm
    elif i == 2:  # Bass (program 38, octaves 1-2)
        set_track_velocity(track, 75)  # Prominent but not overpowering
    elif i == 3:  # Pad (program 88, octaves 2-4)
        set_track_velocity(track, 50)  # Atmospheric background
    elif i == 4:  # Lead (program 80, octaves 4-5)
        set_track_velocity(track, 95)  # Melodic focus (when present)

mid.save(midi_path)

Bassline Patterns

python
# Groovy syncopated house bass
bass_pattern = [
    ('A1', 1.0),      # Downbeat
    ('A1', 0.5),      # Short hit
    ('rest', 0.25),   # Space
    ('A1', 0.25),     # Syncopation
    ('A2', 0.5),      # Octave jump
    ('C2', 0.5),      # Chord tone
    ('A1', 1.0)       # Resolution
]

for pitch, duration in bass_pattern:
    if pitch == 'rest':
        bass_part.append(note.Rest(quarterLength=duration))
    else:
        bass_part.append(note.Note(pitch, quarterLength=duration))

Chord Voicings

python
# Jazz voicing (7th chords)
jazz_chords = [
    ['C4', 'E4', 'G4', 'B4'],   # Cmaj7
    ['D4', 'F4', 'A4', 'C5'],   # Dm7
    ['G3', 'B3', 'D4', 'F4']    # G7
]

# House pad voicing (open, atmospheric)
house_pads = [
    ['A3', 'C4', 'E4'],         # Am
    ['F3', 'A3', 'C4'],         # F
    ['C3', 'E3', 'G3']          # C
]

# Classical voicing (close position)
classical_chords = [
    ['C4', 'E4', 'G4'],         # C major
    ['B3', 'D4', 'G4'],         # G major
    ['C4', 'F4', 'A4']          # F major
]

Melody Construction

python
# Pentatonic scale (versatile, no "wrong" notes)
pentatonic_c = ['C', 'D', 'E', 'G', 'A']

# Major scale
major_c = ['C', 'D', 'E', 'F', 'G', 'A', 'B']

# Minor scale
minor_a = ['A', 'B', 'C', 'D', 'E', 'F', 'G']

# Blues scale
blues_c = ['C', 'Eb', 'F', 'F#', 'G', 'Bb']

# Generate melody algorithmically
for i in range(16):
    octave = 4 + (i // 8)  # Move up octave halfway through
    scale_degree = i % len(pentatonic_c)
    pitch = pentatonic_c[scale_degree] + str(octave)
    melody.append(note.Note(pitch, quarterLength=0.5))

Dynamic Control (Crescendos, Volume Changes)

python
from music21 import dynamics

# Set initial volume
part.insert(0, dynamics.Dynamic('p'))   # Piano (soft)

# Add crescendo at bar 8
part.insert(32, dynamics.Crescendo())   # 32 quarter notes = 8 bars

# Peak at bar 10
part.insert(40, dynamics.Dynamic('ff'))  # Fortissimo (very loud)

# Decrescendo
part.insert(60, dynamics.Diminuendo())

# Return to soft
part.insert(72, dynamics.Dynamic('p'))

# Dynamic markings: ppp, pp, p, mp, mf, f, ff, fff

Timing & Tempo

python
# Set tempo (BPM)
part.insert(0, tempo.MetronomeMark(number=120))  # 120 BPM

# Tempo changes
part.insert(32, tempo.MetronomeMark(number=140))  # Speed up at bar 8

# Timing variations (humanization)
import random
note.Note('C5', quarterLength=1.0 + random.uniform(-0.05, 0.05))

# Common time signatures (set on first part)
from music21 import meter
part.insert(0, meter.TimeSignature('4/4'))  # Most common
part.insert(0, meter.TimeSignature('3/4'))  # Waltz
part.insert(0, meter.TimeSignature('6/8'))  # Compound meter

Complete Example: Deep House Track

python
from music21 import stream, note, chord, tempo
from mido import MidiFile
import subprocess

# 1. Compose with music21
score = stream.Score()
drums = stream.Part()
bass_part = stream.Part()
pad_part = stream.Part()
lead_part = stream.Part()

# Set tempo
drums.insert(0, tempo.MetronomeMark(number=122))

# Add drums using .insert() for proper layering (not .append()!)
bars = 32
beats_per_bar = 4

# Layer 1: Four-on-the-floor kicks
for bar in range(bars):
    for beat in range(beats_per_bar):
        offset = float(bar * beats_per_bar + beat)
        drums.insert(offset, note.Note(36, quarterLength=1.0))

# Layer 2: Snare on beats 2 and 4 of each bar
for bar in range(bars):
    drums.insert(float(bar * beats_per_bar + 1), note.Note(38, quarterLength=1.0))  # Beat 2
    drums.insert(float(bar * beats_per_bar + 3), note.Note(38, quarterLength=1.0))  # Beat 4

# Layer 3: Hi-hats on eighth notes (offbeat open hats for groove)
for bar in range(bars):
    for eighth in range(8):
        offset = float(bar * beats_per_bar) + (eighth * 0.5)
        if eighth % 2 == 0:
            drums.insert(offset, note.Note(42, quarterLength=0.5))  # Closed hat
        else:
            drums.insert(offset, note.Note(46, quarterLength=0.5))  # Open hat (offbeat)

# House BASS: Long sustained notes using .insert() (NOT .append())
bass_offset = 0.0
bass_pattern = [
    ('A1', 32.0),  # A root for 8 bars - 55 Hz (audible on all systems)
    ('E2', 32.0),  # E fifth for 8 bars - 82 Hz
    ('F1', 32.0),  # F for 8 bars - 43.7 Hz
    ('C2', 32.0),  # C for 8 bars - 65.4 Hz
]

for pitch, duration in bass_pattern:
    bass_part.insert(bass_offset, note.Note(pitch, quarterLength=duration))
    bass_offset += duration

# House PADS: Long sustained chords using .insert() (NOT .append())
pad_offset = 0.0
pad_progression = [
    (['A2', 'C3', 'E3'], 64.0),  # Am for 16 bars
    (['F2', 'A2', 'C3'], 64.0),  # F for 16 bars
]

for chord_notes, duration in pad_progression:
    pad_part.insert(pad_offset, chord.Chord(chord_notes, quarterLength=duration))
    pad_offset += duration

# House LEAD: Sparse, long notes, enters late using .insert() (NOT .append())
lead_pattern = [
    ('A4', 8.0),   # 2 bars
    ('C5', 8.0),   # 2 bars
    ('E5', 16.0),  # 4 bars (long sustain)
]

# Lead enters at bar 16 (64 beats in)
lead_offset = 64.0
for pitch, duration in lead_pattern:
    lead_part.insert(lead_offset, note.Note(pitch, quarterLength=duration))
    lead_offset += duration

score.append(drums)
score.append(bass_part)
score.append(pad_part)
score.append(lead_part)

midi_path = '/mnt/user-data/outputs/deep_house_track.mid'
score.write('midi', fp=midi_path)

# 2. Fix instruments with mido (INSERT program_change messages)
from mido import Message
mid = MidiFile(midi_path)

for i, track in enumerate(mid.tracks):
    if i == 1:  # Drums track
        for msg in track:
            if hasattr(msg, 'channel'):
                msg.channel = 9  # Drums must be on channel 9
    elif i == 2:  # Bass track - INSERT program_change
        insert_pos = 0
        for j, msg in enumerate(track):
            if msg.type == 'track_name':
                insert_pos = j + 1
                break
        track.insert(insert_pos, Message('program_change', program=38, time=0))
    elif i == 3:  # Pad track - INSERT program_change
        insert_pos = 0
        for j, msg in enumerate(track):
            if msg.type == 'track_name':
                insert_pos = j + 1
                break
        track.insert(insert_pos, Message('program_change', program=88, time=0))
    elif i == 4:  # Lead track - INSERT program_change
        insert_pos = 0
        for j, msg in enumerate(track):
            if msg.type == 'track_name':
                insert_pos = j + 1
                break
        track.insert(insert_pos, Message('program_change', program=81, time=0))

mid.save(midi_path)

# 3. Render with ELECTRONIC pipeline with deep_house preset!
mp3_path = '/mnt/user-data/outputs/deep_house_track.mp3'

result = subprocess.run([
    'python',
    '/mnt/skills/private/music-generation/scripts/render_electronic.py',
    midi_path,
    mp3_path,
    '--genre', 'deep_house'
], capture_output=True, text=True)

print(result.stdout)
if result.returncode == 0:
    print(f"✓ House track created: {mp3_path}")
else:
    print(f"Error: {result.stderr}")

House Characteristics in This Example:

• Bass: ONE note (A1, E2, F1, C2) held for 8 bars each - deep bass in octave 1-2 (55-82 Hz range, audible on all playback systems)
• Pads: ONE chord held for 16 bars - extreme sustain creates hypnotic atmosphere
• Lead: Sparse (enters bar 16), long notes (2-4 bars each) - not busy
• Repetition: Minimal variation = hypnotic, groovy House feel
• Uses render_electronic.py with deep_house preset for warm, subby synthesis
• Bass synthesized with proper low-end frequencies that consumer audio equipment can reproduce
• Pads use slow attack (0.9s) and long release (1.2s) for smooth transitions
• Genre preset automatically tunes all synthesis parameters
• No external samples or soundfonts needed - fully self-contained

Best Practices

Composition Quality

• Generate variety: Don't repeat the same 4 bars for entire piece
• Use music theory: Real chord progressions, proper voice leading
• Respect instrument ranges: Violin (G3-E7), Cello (C2-C6), Trumpet (E3-C6)
• Add dynamics: Use p, mp, mf, f, ff markings and crescendos
• Structure: Intro → Development → Climax → Resolution
• Add humanization: Vary timing and velocity to avoid robotic sound

python import random n = note.Note('C5', quarterLength=1.0 + random.uniform(-0.05, 0.05)) n.volume.velocity = 80 + random.randint(-5, 5)

Technical Quality

• SoundFont: Use FluidR3_GM.sf2 for best quality
• Bitrate: 192kbps minimum, 320kbps for high quality
• Timing precision: Use quarterLength values carefully
• Cleanup: Remove temporary MIDI/WAV files after MP3 conversion

Common Pitfalls

• CRITICAL: Always use .insert() for ALL tracks - Never mix .insert() and .append(). See "Drum Programming" section for details
• CRITICAL: INSERT program_change messages - Use track.insert(pos, Message('program_change', ...)) not msg.program = X. See mido Quick Reference
• CRITICAL: Set velocities - Lead 90-105, background 50-65. See "Mixing and Balance" section
• CRITICAL: Bass octaves - Use A1-A2 (55-110 Hz), never A0-G0 (inaudible on most systems)
• instrument.Cello() doesn't exist - use Violoncello()
• Forgetting tempo - Add tempo.MetronomeMark() to first part
• Drums not sounding like drums - Set channel to 9 with mido (see mido Quick Reference)

Mixing and Balance

CRITICAL: Setting MIDI program numbers alone is not enough. Without explicit velocity control, some instruments will be completely inaudible.

Setting Velocities

music21 uses default velocity 64 for all notes, which causes poor mixing. Use mido to set velocities after MIDI export:

python
from mido import MidiFile

def set_track_velocity(track, velocity):
    """Set velocity for all note_on messages in a track."""
    for msg in track:
        if msg.type == 'note_on' and msg.velocity > 0:
            msg.velocity = velocity

mid = MidiFile(midi_path)
for i, track in enumerate(mid.tracks):
    if i == 1:  # Drums
        set_track_velocity(track, 75)
    elif i == 2:  # Bass
        set_track_velocity(track, 80)
    elif i == 3:  # Lead instrument (sax, guitar, trumpet)
        set_track_velocity(track, 95)
    elif i == 4:  # Background (organ, pads)
        set_track_velocity(track, 55)
mid.save(midi_path)

Velocity Guidelines

By Role:

• Lead instruments (melody, solos): 90-105
• Rhythm instruments (guitar skanks, comping): 85-100
• Bass: 75-85
• Drums: 70-90
• Background (pads, organs): 50-65

By Frequency Range:

• Low (20-250 Hz): Bass, kick - only ONE dominant at 75-85
• Mid (250-2000 Hz): Most crowded - use velocity to separate (lead 90+, background 50-65)
• High (2000+ Hz): Hi-hats, cymbals - 70-85 for clarity without harshness

Soundfont Level Issues

FluidR3_GM instruments are recorded at different levels. Even with correct velocities, some instruments may be inaudible:

Quiet programs (avoid for lead/rhythm):

• Program 27 (Electric Guitar - clean) - Very quiet
• Program 24 (Acoustic Guitar - nylon)
• Program 73 (Flute)

Better alternatives:

• Program 25 (Acoustic Guitar - steel) - 8-10dB louder, cuts through
• Program 28 (Electric Guitar - muted) - Percussive
• Program 30 (Distortion Guitar) - Aggressive

Additional fixes:

• Increase note duration (0.4 quarterLength minimum vs 0.25)
• Use octave separation (move competing instruments to different octaves)
• Extreme velocity contrast (quiet instrument at 110, loud at 40)

Mixing Checklist

Before rendering:

• ✅ Lead at velocity 90-105
• ✅ Background at velocity 50-65
• ✅ Bass at velocity 75-85
• ✅ Check for quiet instruments (programs 24, 27, 73) and use alternatives
• ✅ Minimum 0.4 quarterLength for rhythm instruments

Resources

• music21 Documentation: https://web.mit.edu/music21/doc/
• General MIDI Spec: https://www.midi.org/specifications-old/item/gm-level-1-sound-set
• Music Theory: https://www.musictheory.net/
• IMSLP (Free Scores): https://imslp.org/ - Download classical MIDIs here!

Limitations

• Instrumental only - No lyrics/vocals
• MIDI-based synthesis - Not studio-quality recordings
• No real-time playback - Files must be rendered before playback
• SoundFont quality - Good but not as realistic as sample libraries

When to Use This Skill

✅ User requests:

• Original compositions with specific moods/styles
• Classical music in MP3 format
• Timed music for videos/presentations
• Specific instrumentation (orchestral, piano, strings, etc.)
• Dynamic music with crescendos, tempo changes

❌ Not suitable for:

• Vocal/lyrical music
• Audio mixing/mastering (reverb, EQ, compression)
• Real-time MIDI playback
• Professional studio recording quality