steelseries-live-scale

Light the notes of a musical scale on a SteelSeries Apex 7 using the GameSense SDK, mapped to Ableton Live's computer MIDI keyboard layout.

Two of the four build steps in apex7-ableton-scale-lighting.md are done:

1. Done — a standalone CLI that lights a scale via GameSense. You pass the scale on the command line; Live is not involved.
2. Done — a Max for Live device that reads the scale from Live's Object Model and prints the computed key set to the Max console. No lighting yet.
3. Next — wire the two together so the board follows Live.
4. Then — polish.

TypeScript, no runtime dependencies. Node 16+.

Quick start (Windows, with SteelSeries GG running)

npm install                       # also compiles src\*.ts to dist\
node bin\apex7-scale.js --root C --scale major

npm install builds via the prepare script; after editing any .ts file run npm run build (or npm run typecheck for types only).

The board dims, the C-major keys light up (A S D F G H J K), the root is orange. The process stays resident and heartbeats so the lighting sticks; you can type new scales at the prompt:

F# dorian
Bb minor-pentatonic
quit

Ctrl+C blanks the board and hands lighting back to SteelSeries GG.

Verify the key mapping on hardware

node bin\apex7-scale.js --key-test

Lights one note key at a time, in order, printing the note it should be. Walk it against the table in the brief — A=C, W=C#, … J=B, K=C (octave up).

Other modes

node bin\apex7-scale.js --demo 2                    # cycle scales, 2s each
node bin\apex7-scale.js --intervals 0,3,5,6,7,10 --root A   # raw intervals (blues)
node bin\apex7-scale.js --once                      # one frame, then exit
node bin\apex7-scale.js --off                       # blank + deregister
node bin\apex7-scale.js --list                      # known scale names
node bin\apex7-scale.js --help

Colors: --bg, --color, --root-color, --off-color, all #rrggbb.

node bin\apex7-scale.js --root D --scale minor --bg "#020208" --color "#ff00d0" --root-color "#ffffff"

How the lighting works

One GameSense event (SCALE) with 14 handlers, all in context-color mode:

Handler	Zone	Frame key
background	every key except the 13 note keys (93 keys)	background
13 × note key	one key each, by HID code	note-a … note-k

Because every handler pulls its color from the event's frame, the handlers are bound once at startup and a scale change is a single POST. That is what step 3 needs when the scale changes mid-set.

Two design notes:

• Zones, not bitmap. The brief suggested bitmap mode. Bitmap's 22×6 grid has no documented index→key table per keyboard model, whereas HID usage codes are exact. Painting all keys with the background zone solves the same problem bitmap was suggested for: the moment a GameSense event arrives the board enters GameSense mode and any key you don't address goes black.
• The octave key K follows pitch class 0 (same as A) but is only tinted as the root when C actually is the root.

Testing without hardware

tools/fake-gamesense.ts stands in for the GameSense server: it accepts the real endpoints, resolves the bound handlers against each frame, and renders the resulting keyboard as ANSI color in the terminal.

npm run stub -- --port 51000                     # terminal 1
node bin/apex7-scale.js --address 127.0.0.1:51000 --root F# --scale dorian   # terminal 2

--address (or GAMESENSE_ADDRESS) skips coreProps.json discovery entirely, so this works on Linux too. --dry-run prints the payloads without sending.

Unit tests for the scale math, key mapping, handler shape and frame colors — plus the LOM parsing and the device's message handling, driven through a fake Max:

npm test

The Max for Live device (step 2)

max/ holds a device that watches Live's scale and prints the keys it computes. It does not light anything yet — that is step 3. Its job is to prove the LOM half of the chain against the mapping table in the brief.

Installing it

The repo ships a .maxpat rather than a .amxd, because an .amxd has to be born inside Live:

1. In Live, drag a Max MIDI Effect onto a MIDI track and click its edit (pencil) button to open Max.
2. Open max/scale-lighting.maxpat in a text editor, copy all of it, then in the Max device window: Edit → Select All, Delete, Edit → Paste. Max pastes the whole patcher, midiin/midiout passthrough included.
3. File → Save, and save the device as max/Ableton Scale Lighting.amxd — in this folder, so js and node.script find their scripts next to it.
4. Make sure dist/ is built (npm install in the repo root). node.script loads dist/src/max/device.js.

Add this repo's folder in Live's browser (Add Folder…) to load the device from there in future sets.

What it prints

Open the Max console (Cmd/Ctrl-Shift-M). Change the scale in Live's control bar and each change prints:

C Major — from the song
  intervals: 0 2 4 5 7 9 11
  notes:     C D E F G A B
  keys:      A S D F G H J K
             A W S E D F T G Y H U J K
             * . * . * * . * . * . * *

The last two lines are every note key in keyboard order with a mark under the lit ones — hold that against the table in the brief and the mapping is verified. The device also sends notes …, keys … and scale … out node.script's outlet, so you can wire them to a live.comment if you want them on the device face.

Which scale it follows

Live 12 puts a scale on the Song and on each clip, so the device supports both. Click the message boxes in the patcher:

• source song (default) — the control bar's global scale.
• source clip — the scale of the clip currently open in the Detail view, falling back to the Song's when no clip is selected or the clip has no scale.
• refresh — re-read and re-send.
• debug 1 / verbose 1 — log every LOM read / every commit, not just changes.

scale_intervals only exists from Live 12.1. On earlier versions the device resolves Live's scale_name against a table of Live's built-in scales (LIVE_SCALE_INTERVALS in src/live.ts); when Live does send intervals, they win, so a scale you edited in Live is followed exactly.

Why the split between js and node.script

LiveAPI exists only inside Max's js/v8 objects — Node for Max cannot see it. So max/scale-observer.js (plain ES5, the one uncompiled file in the repo) observes the LOM and forwards raw values as flat messages, and src/max/device.ts resolves them. That keeps every decision in TypeScript, and means step 3 only has to call ScaleLighting from a place that already has the scale.

Layout

bin/apex7-scale.js      launcher (plain JS) — runs dist/src/cli.js
src/cli.ts              argument parsing, output, the resident stdin loop
src/protocol.ts         GameSense wire types (Rgb, Frame, Handler, …)
src/hid.ts              USB HID usage codes; the full-board key list
src/scale.ts            scale presets, root/interval parsing, pitch class -> QWERTY key
src/gamesense.ts        GameSense REST client (coreProps discovery, heartbeat, cleanup)
src/lighting.ts         handler + frame construction
src/errors.ts           `catch (err: unknown)` helpers
src/index.ts            ScaleLighting — the API step 3 will call from Node for Max
src/live.ts             LOM values -> a resolved scale, and how to print it
src/max/device.ts       the Node for Max device: messages in, key set out
max/scale-lighting.maxpat  the M4L patcher (paste into a device created in Live)
max/scale-observer.js   the `js` object that observes the Live Object Model (ES5)
max/scale-device.js     `node.script` launcher — runs dist/src/max/device.js
tools/fake-gamesense.ts terminal simulator of the GameSense server
test/logic.test.ts      unit tests for the lighting half
test/live.test.ts       unit tests for the Live half, with a fake Max
dist/                   compiled CommonJS + .d.ts (gitignored)

tsconfig.json emits CommonJS at ES2020, because Node for Max loads CJS on a Node version we do not control.

What step 3 has to do

Both halves now exist and neither knows about the other. Step 3 is joining them inside src/max/device.ts: it already resolves a LiveScale on every commit, so it needs to hold a ScaleLighting, start it on load, call showScale(scale.root, scale.intervals) where it currently prints, and stop it on notifydeleted. src/index.ts is that seam — no CLI concerns in it, and it ships type declarations alongside the compiled JS:

import { ScaleLighting } from 'steelseries-live-scale';
// or, from a Node for Max script: require('<repo>/dist/src')

const lights = new ScaleLighting();
await lights.start();                        // register + bind + heartbeat
await lights.showScale(0, [0,2,4,5,7,9,11]); // root_note + scale_intervals from the LOM
// ...
await lights.stop();

showScale(root, intervals) takes exactly what Live 12's Song object exposes as root_note and scale_intervals.

Troubleshooting

• coreProps.json not found — SteelSeries GG isn't running, or is installed somewhere unusual. Expected at %PROGRAMDATA%\SteelSeries\SteelSeries Engine 3\coreProps.json.
• Nothing lights up — check GG's Engine is enabled and that no other app holds an exclusive lighting profile.
• Lighting reverts after ~15s — that's GameSense's deactivation timeout; it only happens with --once, since resident mode heartbeats every 5s.
• A key stays dark — it may not be in src/hid.ts. Add its HID code there; keys not addressed by any handler go black in GameSense mode.
• apex7-scale is not built yet — run npm run build.
• The device prints nothing — the Max console should show scale: ready on load. If not, node.script never started: check dist/src/max/device.js exists, and that the .amxd was saved in max/ next to the two scripts.
• scale: no scale yet — live.thisdevice never banged, or Live has no scale set. Click refresh in the patcher.
• Nothing changes when you pick a clip — the device follows the Song by default; click source clip.