accompy 0.0.4

Generate backing track audio from chord charts

accompy 🎵

Generate backing track audio from chord charts in Python — like iReal Pro, but scriptable.

from accompy import generate_accompaniment

# Generate a bossa nova backing track
audio = generate_accompaniment("| Dm7 | G7 | C^7 | A7b9 |", style="bossa", tempo=140)
print(f"Generated: {audio}")  # -> /tmp/xxx.wav

Features

• Simple API: One function to generate complete backing tracks
• Multiple styles: Swing, bossa nova, rock, funk, ballad, latin, waltz, blues
• iReal Pro compatible: Parse iReal Pro URLs directly
• Multi-instrument: Drums, bass, piano with style-appropriate patterns
• Audio output: WAV, MP3, FLAC via FluidSynth
• Extensible: Add custom patterns and styles

Quick Start

Installation

pip install accompy  # Coming soon to PyPI

# Or install from source:
git clone https://github.com/yourname/accompy
pip install -e accompy

System Dependencies

accompy requires FluidSynth and a SoundFont for audio rendering.

Automated Setup (Recommended)

The easiest way to get started:

# Install accompy
pip install -e .

# Run automated setup (interactive)
python -c "from accompy import verify_and_setup; verify_and_setup()"

# This will:
# - Check all dependencies
# - Offer to install missing ones (with your permission)
# - Download and configure SoundFont files
# - Verify everything works

Manual Setup

If you prefer to install manually:

# macOS
brew install fluid-synth
# FluidSynth 2.5+ comes with a bundled SoundFont
# The setup will automatically link it for you

# Ubuntu/Debian
sudo apt-get install fluidsynth fluid-soundfont-gm

# Install Python dependencies
pip install midiutil mingus

# Verify setup
python -m accompy --check-deps

Check Your Setup

# Quick check
python -c "from accompy import check_dependencies; print(check_dependencies())"

# Detailed diagnostic report
python -c "from accompy import print_diagnostic_report; print_diagnostic_report()"

Usage

Basic Usage

from accompy import generate_accompaniment

# Generate with default settings
audio = generate_accompaniment("| C | Am | F | G |")

# Specify style and tempo
audio = generate_accompaniment(
    "| Dm7 | G7 | Cmaj7 | Am7 |",
    style="swing",
    tempo=160,
    repeats=4,
    output_path="my_track.wav"
)

Using Score Objects

For more control, create a Score object:

from accompy import Score, generate_accompaniment

# Parse chord string
score = Score.from_string(
    "| Dm7 | G7 | Cmaj7 | % |",  # % = repeat previous chord
    title="ii-V-I in C",
    key="C",
    time_signature=(4, 4)
)

# Generate audio
audio = generate_accompaniment(score, style="swing", tempo=120)

Chord Notation

accompy supports flexible chord notation:

# Jazz notation (iReal Pro style)
"| C^7 | D-7 | G7 | C^7 |"   # ^7=maj7, -7=min7

# Standard notation  
"| Cmaj7 | Dm7 | G7 | Cmaj7 |"

# Simple notation
"| C | Dm | G | C |"

# Multiple chords per bar
"| Dm7 G7 | Cmaj7 |"  # Two chords, split evenly

# Repeat symbols
"| C | G | % | F |"   # % repeats G

Chord symbol reference:

Notation	Meaning
C, Cmaj	C major
C-, Cm, Cmin	C minor
C7	C dominant 7
C^7, Cmaj7	C major 7
C-7, Cm7, Cmin7	C minor 7
Co, Cdim	C diminished
Co7, Cdim7	C diminished 7
Ch7, Cm7b5	C half-diminished
C+, Caug	C augmented
Csus, Csus4	C suspended 4th

Styles

Available styles with characteristic patterns:

Style	Description	Typical Tempo
swing	Jazz swing with walking bass	120-200 BPM
bossa	Bossa nova with syncopated feel	100-150 BPM
rock	Straight 8ths rock beat	100-140 BPM
funk	Syncopated funk groove	90-120 BPM
ballad	Slow, sustained ballad	60-90 BPM
latin	Latin/salsa with clave	100-130 BPM
waltz	3/4 waltz pattern	90-150 BPM
blues	Blues shuffle	80-120 BPM

iReal Pro Integration

Parse and play iReal Pro chord charts:

from accompy import Score, generate_accompaniment

# From iReal Pro URL (copy from app or forum)
url = "irealb://6dim=Composer%20Unknown==Medium%20Swing=C=7=1r34LbKcu7QyX%2DA6XyQ%7C%23G%7CQyXG%2F6C%7CQyXFo%7CQyXE%2F6C%7CQyXoDoXyQ%7CC44T%7BXQyXQQ%7DXyQQyXQyXQyXQyXQyQXyXQyXQyXQyXQyXXyQXyyXoB%7CQyXQyXyQXyyXQyXQyXQyXQyXyQXQyXQyXQyXQyXQQXyQXQyXQyyXQyXQXyQXXQyXQyXQyXQyXQXyQyXQyXQyXQyXQyyQXyQyXQyXQXyQXyQXyQXyQXyQ%20Z%20=Jazz%2DMedium%20Up%20Swing%202=118=21]6dim"
score = Score.from_ireal_url(url)

# Generate backing track
audio = generate_accompaniment(score, style="swing", tempo=140)

Note: Requires pyRealParser: pip install pyRealParser

Advanced Configuration

Full control with AccompanimentConfig:

from accompy import AccompanimentConfig, generate_accompaniment

config = AccompanimentConfig(
    style="swing",
    tempo=160,
    repeats=4,
    instruments={
        "drums": True,
        "bass": True,
        "piano": True,
        "guitar": False,
    },
    volumes={
        "drums": 0.7,
        "bass": 1.0,
        "piano": 0.6,
    },
    sample_rate=44100,
    output_format="mp3",  # wav, mp3, flac
)

audio = generate_accompaniment(
    "| Dm7 | G7 | Cmaj7 | A7 |",
    config=config,
    output_path="backing_track.mp3"
)

Command Line

# Generate backing track
python -m accompy "| C | Am | F | G |" -s bossa -t 120 -o track.wav

# Check dependencies
python -m accompy --check-deps

# Options
python -m accompy --help

How It Works

1. Parse chords: Convert chord string → Score object with normalized chord symbols
2. Generate MIDI: Create multi-track MIDI with drums, bass, piano patterns
   • Uses MMA (Musical MIDI Accompaniment) if available for realistic tracks
   • Falls back to built-in pattern generator
3. Render audio: Convert MIDI → WAV using FluidSynth with SoundFont
4. Convert format: Optionally convert to MP3/FLAC via ffmpeg or pydub

MMA (Musical MIDI Accompaniment)

For the best quality backing tracks, install MMA:

# MMA provides 50+ professionally designed grooves
git clone https://github.com/infojunkie/mma
cd mma && python install  # Follow MMA installation instructions

MMA offers extensive groove libraries with realistic fills, variations, and transitions.

Python Dependencies

Required:

• midiutil — MIDI file generation

Recommended:

• mingus — Music theory (better chord parsing)
• pyRealParser — iReal Pro URL parsing
• pydub — Audio format conversion (if no ffmpeg)

pip install midiutil mingus pyRealParser pydub

API Reference

generate_accompaniment(chords, *, style, tempo, repeats, output_path, config, use_mma)

Generate accompaniment audio from chord progression.

Parameters:

• chords (str | Score): Chord progression
• style (str): "swing", "bossa", "rock", "ballad", "funk", "latin", "waltz", "blues"
• tempo (int): BPM (default: 120)
• repeats (int): Number of times through the form (default: 2)
• output_path (str | Path): Where to save audio (default: temp file)
• config (AccompanimentConfig): Full config (overrides style/tempo/repeats)
• use_mma (bool): Use MMA if available (default: True)

Returns: Path to generated audio file

Score.from_string(chord_string, *, title, key, time_signature)

Parse chord string into Score object.

Score.from_ireal_url(url)

Parse iReal Pro URL into Score object.

check_dependencies()

Returns dict of available dependencies.

print_setup_instructions()

Print installation instructions for missing dependencies.

Troubleshooting

Common Issues

"No SoundFont found" Error

Problem: RuntimeError: No SoundFont found. Download FluidR3_GM.sf2 and place in ~/.fluidsynth/default_sound_font.sf2

Solutions:

1. Automated fix:

   python -c "from accompy import setup_soundfont; setup_soundfont()"
   

2. Check if FluidSynth includes a SoundFont:

   # macOS with Homebrew
   find /opt/homebrew/Cellar/fluid-synth -name "*.sf2"
   

   If found, run the automated setup to link it.

3. Manual download:

   mkdir -p ~/.fluidsynth
   # Download MuseScore General (high quality, 35MB)
   curl -L -o ~/.fluidsynth/default_sound_font.sf2 \
     "https://ftp.osuosl.org/pub/musescore/soundfont/MuseScore_General/MuseScore_General.sf2"
   

4. Verify the file:

   ls -lh ~/.fluidsynth/default_sound_font.sf2
   # Should be several MB (not just a few bytes)
   

"FluidSynth not found" Error

Problem: RuntimeError: FluidSynth not found. Install with: brew install fluidsynth

Solutions:

1. macOS:

   brew install fluid-synth
   

2. Ubuntu/Debian:

   sudo apt-get update
   sudo apt-get install fluidsynth
   

3. Windows: Download from FluidSynth releases and add to PATH

4. Verify installation:

   which fluidsynth
   fluidsynth --version
   

SoundFont File is Corrupted (255 bytes)

Problem: Downloaded SoundFont is tiny (255 bytes) and appears to be XML

Cause: Download URL redirected to an error page

Solution:

# Remove corrupted file
rm ~/.fluidsynth/default_sound_font.sf2

# Use automated setup
python -c "from accompy import setup_soundfont; setup_soundfont(force=True)"

# Or manually download from a reliable source
curl -L -o ~/.fluidsynth/default_sound_font.sf2 \
  "https://ftp.osuosl.org/pub/musescore/soundfont/MuseScore_General/MuseScore_General.sf2"

Import Warning About Missing Dependencies

Problem: Warning on import: accompy setup incomplete - missing: fluidsynth, soundfont

Solutions:

1. Run setup:

   python -c "from accompy import verify_and_setup; verify_and_setup()"
   

2. Temporarily disable warning:

   export ACCOMPY_SKIP_SETUP_CHECK=1
   python your_script.py
   

3. Fix manually and verify:

   # Install dependencies
   brew install fluid-synth  # or apt-get install fluidsynth
   pip install midiutil
   
   # Run diagnostic
   python -c "from accompy import print_diagnostic_report; print_diagnostic_report()"
   

"midiutil not found" Error

Problem: Missing Python dependency

Solution:

pip install midiutil mingus

Diagnostic Tools

Run Full Diagnostic

Get a comprehensive report of your setup:

from accompy import print_diagnostic_report
print_diagnostic_report()

This shows:

• System information
• Dependency status (✓ or ✗)
• Specific issues found
• Solutions for each issue

Check Specific Issues

from accompy import diagnose_issues

for issue, description, solution in diagnose_issues():
    print(f"Issue: {issue}")
    print(f"Description: {description}")
    print(f"Solution: {solution}\n")

Verify Individual Dependencies

from accompy import check_dependencies

deps = check_dependencies()
print(f"FluidSynth: {deps['fluidsynth']}")
print(f"SoundFont: {deps['soundfont']}")
print(f"midiutil: {deps['midiutil']}")
print(f"mingus: {deps['mingus']}")
print(f"MMA: {deps['mma']}")

Getting Help

If you're still having issues:

1. Run diagnostic report and save output:

   python -c "from accompy import print_diagnostic_report; print_diagnostic_report()" > diagnostic.txt
   

2. Check existing issues: GitHub Issues

3. Create a new issue with:

   • Your diagnostic report
   • What you tried
   • Full error message

Contributing

Contributions welcome! Areas of interest:

• Additional styles/grooves
• Better drum fills and variations
• Improved chord voicings
• More instrument parts (guitar, strings, horns)
• Web interface
• Better cross-platform setup automation

License

MIT

Acknowledgments

• MMA - Musical MIDI Accompaniment by Bob van der Poel
• FluidSynth team
• pyRealParser for iReal Pro format parsing
• iReal Pro for inspiration