mobygratis

An Ableton Live extension for browsing and importing tracks from MobyGratis directly into your Live Set.

Architecture

Extension Host

• Entry: src/extension.ts, bundled to dist/extension.js
• Registers a context-menu action "MobyGratis: browse & import" on scopes: AudioClip, AudioTrack, MidiTrack, ClipSlot, Scene
• Opens a WebView modal dialog served from a local HTTP server (http://127.0.0.1:PORT/)
• All HTTP requests to MobyGratis APIs are proxied through the local server (ExtensionHost sandbox strips Web API globals like fetch, URL, URLSearchParams)

Local HTTP Server

Created in startServer() on a random port. Endpoints:

Method	Path	Purpose
GET	/	Serves the dialog HTML (replaces __API_BASE__ placeholder)
GET	/api/tracks	Lists audio tracks in the Live Set (filtered via native getObjectIsOfClass)
GET	/api/auth-status	Returns { signedIn, email } from stored Firebase idToken
POST	/api/verify-magic-link	Verifies Firebase email magic link, stores idToken
POST	/api/sign-out	Clears auth token
GET	/api/preview/<uuid>	Proxies to https://mobygratis.com/api/preview/<uuid> with Bearer token, returns pre-signed audio URL as plain text
POST	/api/search	Proxies to https://mobygratis.com/api/search

Authentication

• Firebase email magic link auth via Identity Toolkit REST API (accounts:sendOobCode + accounts:signInWithEmailLink)
• Token stored as module-level authToken (non-anonymous Firebase idToken)
• Anonymous tokens rejected by MobyGratis server

Track Import Flow

1. User clicks Import in the dialog
2. Dialog sends { action: "import", slug, uuid, format } via closeWithResult
3. importTrack() calls POST https://mobygratis.com/api/fetch with id=<uuid>&format=WAV + Bearer token
4. Parses response HTML for <a href="..."> to get pre-signed Cloudflare R2 download URL
5. Downloads audio file via getFile() (supports RIFF/WAV and FORM/AIFF)
6. Imports into Live project via context.resources.importIntoProject()
7. Creates session clip: tries selected track's first empty clip slot; falls back to creating a new audio track
8. All steps wrapped in withinProgressDialog with abort support

Track Preview

• Play button (▶) in track listing fetches GET /api/preview/<uuid> → proxies to https://mobygratis.com/api/preview/<uuid> with Bearer token → returns pre-signed Cloudflare R2 audio URL
• URL is set on a hidden <audio> element in the WebView for playback
• Clicking the same button again stops playback; clicking another track switches playback
• Requires sign-in (same as import)

Key SDK Quirks

ExtensionHost Sandbox

Node.js globals stripped: fetch, URL, URLSearchParams, AbortController. Use node:https for HTTP, manual URL parsing via parseUrl(), custom query-string building via qs().

Track Type Resolution

Live 12 beta resolves existing audio tracks as Track base class (not AudioTrack) — getObjectIsOfClass(handle, "AudioTrack") returns false for pre-existing tracks. Freshly-created tracks via song.createAudioTrack() DO resolve as AudioTrack.

Workaround: filter tracks by calling dataModel.getObjectIsOfClass() directly, and fall back to creating a new track if clip slot creation fails on the selected track.

File Format Detection

Some MobyGratis tracks return AIFF (starts with FORM) instead of WAV (RIFF). The download saves with .aiff extension and Live imports it correctly.

Firebase

• API key: AIzaSyCTwaxUqAP88DzfAkhVaaYAdpmfl_hh5wc
• Auth domain: mobygratis-2945d.firebaseapp.com
• Uses identitytoolkit.googleapis.com/v1 REST endpoints

Build & Run

npm run build         # production bundle
npm run build:dev     # dev bundle with sourcemaps
npm start             # build + run in Extension Host
npm run package       # build + create .ablx archive

Extension Host path: /Applications/Ableton Live 12 Beta.app/Contents/Helpers/ExtensionHost/ExtensionHostNodeModule.node

Dependency Versions

• @ableton-extensions/sdk: ^1.0.0-beta.0
• Node.js: >=24.14.1
• ESM project (TypeScript), CJS bundle via esbuild (platform: node, format: cjs)
• HTML inlined via esbuild loader: { ".html": "text" }