logicx

Read Logic Pro projects from Go, and export them as MusicXML.

This is unofficial and reverse-engineered, not affiliated with or endorsed by Apple. Apple documents none of the format, so everything here is best effort, worked out from real projects: it decodes what has been figured out, skips what it does not recognise, and can be wrong or incomplete for projects, plug-ins or Logic versions it has not met. Read an exported score against the project before trusting it, and expect a Logic update to be able to break the parsing. Nothing here ever writes to a bundle, but keep backups of irreplaceable projects anyway.

MusicXML Bridge for Logic Pro

./install.sh

builds MusicXML Bridge for Logic Pro.app into ~/Applications and links the command, logicx-to-musicxml, into $HOME/bin. APP_DIR and BIN_DIR override both; uninstalling is deleting them.

Save the Logic project, then choose Logic Pro > Services > Export to MusicXML, which exports the project Logic has open — it asks Logic which one that is, so the first run wants permission to do so. Every other way in names its own project: drop one on the app, open one with the app, or open the app by itself and it asks which. The app provides that menu item itself: Logic's Scripter plug-in cannot launch programs, but every app's Services menu can. Opening the app by hand offers an Add to Logic Pro Menu button that registers it, and System Settings > Keyboard > Keyboard Shortcuts > Services will give it a shortcut.

A dialog offers the quantization grids, triplet detection, the chord and MIDI options, and the project alternative when there is more than one. Export… asks where to save, writes the files, and reveals them in Finder. The score is read from the project file, so unsaved changes are not in it; the dialog says as much when Logic reports the project as modified.

The app is the same binary as the command: with arguments it is a command, without them it is the app.

Command line

logicx-to-musicxml -o score.musicxml song.logicx

flag	default
-o	stdout	where the score is written
-alternative	first	which project alternative to export
-quantize	1/16	coarsest grid notes snap to; off keeps Logic's timing
-quantize-chords	1/4	grid chord symbols snap to; off keeps theirs
-triplets	true	notate beats played in thirds as triplets
-realize-chords	false	voice chord staves as pitches, not rhythm slashes
-midi	false	also write the raw notes beside -o as a MIDI file
-ui	false	ask for the settings in the dialog

-midi is worth knowing about: notation programs quantize and detect tuplets on import better than a grid snap here can, and the MusicXML alongside carries the chord symbols, sections and layout that MIDI cannot express.

What the export carries

Parts. Sequences sharing a Logic name merge into one part. Overlapping notes are spread across voices, and silence in the first voice becomes rests.

Maps. Tempo, key and time signatures are reconstructed, asymmetric beat grouping included. Markers become bold system text and close the preceding bar with a double barline — deliberately not rehearsal marks, which notation programs renumber into their own A, B, C and so lose the section name.

Chords. Region chords stay on their own sequence; project chords join a staff that already plays them, or get a Project Chords staff. They are written as semantic MusicXML harmony elements, and land on their own grid, since a chord change belongs on the beat however loosely it was played. A staff with no recorded notes becomes a chord chart, one rhythm slash per beat.

Timing. Notes snap to a notation grid, refined automatically where they crowd closer than it, and durations split into tied notatable values, so raw performance data — a Melodyne transcription, say — still reads. A beat whose notes fit thirds better than the straight grid is written as a triplet. Turning quantization off turns detection off with it, since it works by measuring how far onsets sit off a grid there no longer is.

Notation. Staff notes are spelled from the key signature, or from the chord track where the key is the C major Logic starts out with. Region placement, right-edge cropping and loops are reconstructed, with looped notes, region chords, tempo curves, lyrics and score articulations expanded. Performance articulation-ID assignments stay in the raw chunks, undecoded.

Library

bundle, err := logicx.OpenBundle("song.logicx")
if err != nil {
	log.Fatal(err)
}
fmt.Println(bundle.Alternatives[0].Metadata.BPM)
fmt.Println(bundle.PropertyLists["Resources/ProjectInformation.plist"])
fmt.Println(bundle.Alternatives[0].Project.Sequences[0].Notes[0].Pitch)

Every plist value (binary ones without an extension included) and every raw ProjectData chunk is exposed, alongside decoded metadata, channel strips, Audio Units, MIDI sequences, score articulations, markers, tempo maps and key/time signatures. ParseProjectData and ParseMetadata take bytes, for a boundary that touches no files.

---

Building, releasing and how the app bundle is put together: DEVELOPMENT.md. The vocabulary the score reconstruction uses: CONTEXT.md.

Format knowledge is based on lpx-toolkit and lpx-explorer. Logic Pro is a trademark of Apple Inc.

License: GPL-3.0-or-later.