Audio to MIDI

Audio-to-MIDI Transcription

Convert audio files to MIDI and MusicXML with full music analysis (tempo, key, chords, dynamics, instruments).

Tool

Script: scripts/transcribe.py -- wraps Basic Pitch, Demucs, librosa, and music21. Auto-installs dependencies.

Workflow

1. Identify the input audio file (MP3, WAV, FLAC, OGG, M4A)
2. Determine options:
   • Stems? Add --stems to separate vocals/drums/bass/other with Demucs first
   • Output dir? Use -o path or default to input file's directory
   • Skip analysis? Add --no-analysis if only MIDI/MusicXML needed
   • Skip MusicXML? Add --no-musicxml if only MIDI needed
3. Run the transcription script
4. Report output files and analysis summary to user

Engines

Engine	Flag	Best for	Accuracy
Basic Pitch	--engine basic-pitch (default)	Mixed/polyphonic music	Good
Piano Model	--engine piano	Piano/keyboard music	96.7% F1

For piano or keyboard music, always use --engine piano — it captures sustain/pedal, has far fewer ghost notes, and produces much more accurate MIDI.

Usage

bash

# Piano music (recommended for piano/keyboard)
py -3.12 scripts/transcribe.py "piano.mp3" --engine piano

# General music (default engine: Basic Pitch)
py -3.12 scripts/transcribe.py "song.mp3"

# With stem separation (Demucs): each stem gets its own MIDI + MusicXML
py -3.12 scripts/transcribe.py "song.wav" --stems

# Custom output directory
py -3.12 scripts/transcribe.py "song.mp3" -o ./output --engine piano

# Tuning Basic Pitch sensitivity
py -3.12 scripts/transcribe.py "song.mp3" --onset-threshold 0.6 --frame-threshold 0.4

# MIDI only (skip MusicXML)
py -3.12 scripts/transcribe.py "song.mp3" --no-musicxml

# MIDI + MusicXML without analysis
py -3.12 scripts/transcribe.py "song.mp3" --no-analysis

Output Files

For input song.mp3:

• song.mid -- MIDI file (for DAWs, notation software)
• song.musicxml -- MusicXML (for MuseScore, Finale, Sibelius, Dorico)
• song_analysis.json -- Full analysis (tempo, key, chords, dynamics, spectral)

With --stems, each stem produces its own MIDI + MusicXML:

• vocals.mid, vocals.musicxml
• drums.mid, drums.musicxml
• bass.mid, bass.musicxml
• other.mid, other.musicxml

Analysis Output

The _analysis.json contains:

• tempo_bpm: Detected BPM
• key: Detected key and mode (e.g. "A minor")
• key_confidence: 0-1 confidence score
• chords: Time-stamped chord progression
• unique_chords: Deduplicated chord list
• dynamics: Mean/max/min dB, dynamic range
• spectral: Centroid, bandwidth, rolloff, ZCR
• instrument_hints: Detected instrument categories

Tuning Parameters

Flag	Default	Effect
--onset-threshold	0.5	Higher = fewer ghost notes, may miss quiet notes
--frame-threshold	0.3	Higher = stricter note detection
--min-note-length	58	Minimum note duration in ms

For clean recordings (piano, guitar): defaults work well. For complex mixes: use --stems for best results. For percussive music: lower onset threshold to 0.3-0.4.

Dependencies

Auto-installed on first run: basic-pitch, librosa, music21, pretty_midi, numpy, onnxruntime. With --stems: also installs demucs (includes PyTorch). Requires: Python 3.12 (py -3.12), ffmpeg (for MP3 decoding).

Important: Use py -3.12 (not python) to run the script. Python 3.14 has compatibility issues with ML packages. The script auto-selects the ONNX backend for Basic Pitch (most compatible).

Supported Input Formats

MP3, WAV, FLAC, OGG, M4A, AAC, WMA