MusicXML to MIDI converter

A suite of tools to convert MusicXML scores to MIDI using Musical MIDI Accompaniment (MMA).

Installation

• Install xmllint (included in libxml2 on most platforms)
• git submodule update --init --recursive
• npm install && npm run build

Convert a MusicXML score to MIDI

• npm run --silent convert:unroll song.musicxml > song-unrolled.musicxml to unroll a MusicXML score by expanding all jumps and repeats
• npm run --silent convert:mma song.musicxml > song.mma to both unroll a score and convert it to an MMA script
• npm run --silent convert:groove groove-name [chords="A,B,C"] [tempo=X] [count=Y] [keysig=Z] > groove.mma to generate a groove MMA script
• npm run convert:midi /path/to/song.mma to convert an MMA script to MIDI file at /path/to/song.mid
• npm run --silent convert:timemap song.musicxml > song.timemap.json to convert a score to a timemap JSON file

Serve a conversion API endpoint

• PORT=3000 npm run develop for development (including hot-reload)
• PORT=3000 npm run start for production
• curl -sSf -F"musicXml=@test/data/salma-ya-salama.musicxml" -F"globalGroove=Maqsum" http://localhost:3000/convert -o "salma-ya-salama.mid"
• curl -sSf -F"groove=Maqsum" -F"chords=I, vi, ii, V7" -F"count=8" http://localhost:3000/groove -o "maqsum.mid"
• curl -sSf -F"jq=.[] |= {groove,description,timeSignature}" http://localhost:3000/grooves.json

Other operations

• Convert a MIDI file to a timemap JSON file: ./src/js/midi-timemap.js song.mid > song.timemap.json
• Scrape MusicXML examples from the official site: ./src/js/musicxml-examples.js --output=./test/data/examples
• Convert MMA grooves to MusicXML: ./src/js/musicxml-grooves.js --output=./test/data/grooves
• Convert MIDI to JSON and back: ./src/js/midi-json.js < source.mid | jq [..] | ./src/js/midi-json.js > target.mid

Theory of operation

This converter aims to create a valid MMA accompaniment script out of a MusicXML score. The MMA script is then converted to MIDI using the bundled mma tool. To accomplish this, the converter expects to find the following information in the sheet:

• Chord information, expressed as harmony elements. MMA recognizes a large number of chords, but MusicXML's harmony representation is more general and can lead to invalid chord names. Refer to chords.musicxml for a reference on how to express all MMA-supported chords.

• Melody information, expressed as note elements. This is converted to an MMA SOLO sequence for each measure.

• Optional playback style information, expressed as sound/play/other-play elements with attribute @type = 'groove'. The content of this element represents the "groove" that is passed to MMA to generate an accompaniment. In case no such playback style information is found, or the specified style is not mapped to an existing MMA groove, the chords are played back as per the lead sheet without further accompaniment. Note that several styles can be specified in a single sheet, since the sound element is associated with measure or measure/direction elements. The groove can be overridden with the argument globalGroove.

The produced MMA script / MIDI file contains metadata that can be useful to downstream consumers. This metadata is generally expressed as MIDI Marker meta messages, with the following syntax:

• Measure:N:T informs the consumer that the MIDI playback has reached measure N (0-based) with duration T milliseconds.
• Groove:X informs the consumer that the MIDI playback is henceforth using the specified playback style.

The tools contained here can also convert the score (or the generated MIDI file) to a so-called Timemap JSON file, which lists timing information for each measure:

[
  {
    // 0-based measure index (integer)
    measure: number,

    // 0-based offset in milliseconds (real)
    timestamp: number,

    // duration in milliseconds (real)
    duration: number
  },
  // ...
]