Chord Display

A Schwung audio FX for the Ableton Move that shows the chord being played, by the pads or by a clip, on any track, with its roman numeral in the Set's key.

C major with E in the bass, in a C Major Set. Drawn by the module's own page code at 4x; Move's screen is 128x64.

No settings to tune: one Channel setting, and the display keeps the last chord until the next one. A single note, or two notes that are not a power chord, clears it.

Setup

1. Load Chord Display as an audio FX on any Schwung slot. It leaves the audio and the slot's MIDI untouched.
2. Set each Move track's MIDI Out to a channel (Shift + Track) so Schwung sees its notes.
3. Pick Channel:
   • Auto (default): the slot's own receive channel. If the slot listens to All, everything is read.
   • 1-16: that channel only. Put the module on the bass track's slot and pick the chord track's channel to see its chords while you edit the bass.
   • Omni: every channel.
4. Open the slot in Schwung: the chord is on the first page.

It does not draw over Move's own screen; you see the chord on its page in the Schwung editor.

How it reads

• Audio FX receive the notes of every channel with their channel number, which is why this is an audio FX and not a MIDI FX.
• Pad presses on Move's own surface can reach audio FX as pad numbers (68-99) on channel 1. Prefer a channel other than 1 for the chord track.
• Inversions show a slash in both rows: the bass note in the name (C/E), its scale degree in the key in the numeral (I/3). A bass outside the scale is named from its place in the chord: D/F# in C Major is II/#4.
• The numeral uses the Set's root note and scale, read from Move. Notes outside the scale get b or #. Unknown scales use chromatic numerals; with no key, only the name is shown.
• The chord and its numeral each get a row, in two fixed sizes (the numeral is smaller); long names never shrink or wrap.

Build and test

node --test test/chords.test.mjs                                          # naming, numerals, layout
cc -Isrc/dsp -o /tmp/dsp_test test/dsp_test.c -ldl && /tmp/dsp_test       # note latching, channels
cc -Isrc/dsp -o /tmp/dsp_clock_test test/dsp_clock_test.c -ldl && /tmp/dsp_clock_test   # the real clock
./scripts/build.sh                                                        # Docker, writes dist/chord-display-module.tar.gz

Needs Schwung 1.6.2 or newer, tested on 1.7.3: 1.6.0 added move_info.h (the key) and 1.6.2 lets the chord page come first.

Credits

• Schwung (MIT, Charles Vestal): the three host headers in src/dsp are copied unchanged, and the host docs and source are what this module is built against.
• schwung-ducker (MIT, Charles Vestal): the build script, Dockerfile, release workflow and the audio FX entry points are adapted from it. Ducker also showed that an audio FX hears every MIDI channel.
• ChordDex (MIT, dony01001): the idea of naming a chord by matching the held notes against a table of chord shapes, preferring the reading rooted on the bass note and showing the bass as a slash (C/E). The chord table, scoring and code here are written from scratch; no code was copied.
• Chordism and Impressive Chords were looked at for comparison; nothing was taken from them.

Copied and adapted parts are listed with their license in THIRD_PARTY_LICENSES.md.

AI disclosure

This module was written with the help of AI: Claude (Anthropic; models Claude Opus 5.5 and Claude Sonnet 5.5). The author reviews the results and directs the project.