AbleVSEP

Right-click an audio clip in Ableton Live → Separate Stems with MVSEP → pick any mvsep.com model → the stems come back as new, group-styled tracks. It mirrors Live's built-in Stem Separation workflow, but exposes mvsep's full model catalog (126+ models) instead of one fixed algorithm.

Unofficial. AbleVSEP is not affiliated with, endorsed by, or sponsored by Ableton or MVSEP.

Features

• Separate an Arrangement audio clip or a Session clip slot into stems.
• Choose any mvsep model from a searchable picker, with that model's variant options.
• Stems land as new adjacent tracks named <clip> - <stem>, each in its own track color for easy visual separation, with the original muted (press ⌘G to fold them into a group).

How it works

The extension renders/reads the clip's audio, uploads it to mvsep's separation API with your chosen model, polls until the job finishes, downloads the stems, and places them back into your set.

Install

Download the latest .ablx from the Releases page (or build one, see Build from source), then:

1. In Ableton Live, open Preferences → Extensions (with Developer Mode off, so Live manages the extension).
2. Drag the .ablx onto that page.
3. Right-click an audio clip → Separate Stems with MVSEP.

Usage

1. Right-click an audio clip (Arrangement) or a Session clip slot → Separate Stems with MVSEP.
2. Search/select a model, set its options + output format, paste your mvsep API token (optionally "remember as default"), click Separate.
3. Stems arrive as new tracks named <clip> - <stem>, each in its own track color, with the original muted.
4. To group them: select the new tracks and press ⌘G (Live's extension API can't create a group track programmatically).

Requirements

To install and use:

• Ableton Live Suite 12.4.5+ with Extensions enabled (tested on Ableton Beta 12.4.5b3). The .ablx is self-contained and runs inside Live's Extension Host.
• An mvsep API token, see https://mvsep.com/full_api.

To build from source (development only):

• Node.js ≥ 24.
• The Ableton Extensions SDK (beta), distributed by Ableton and not included in this repository (see below).

Build from source

This project depends on the Ableton Extensions SDK, which is not published to npm and is not bundled here. Obtain it from Ableton, then:

1. Download and unpack the Extensions SDK (e.g. extensions-sdk-1.0.0-beta.0).
2. Tell the project where it is and install:

   cp .env.example .env
   # set ABLETON_SDK_PATH to your unpacked SDK, e.g. /path/to/extensions-sdk-1.0.0-beta.0
   npm run setup

   npm run setup copies the SDK tarballs into ./vendor/ (git-ignored) and installs all dependencies. Set the path once and you never edit package.json.

Develop

The fastest loop uses Live's Developer Mode and an externally-launched Extension Host:

1. In your .env, set EXTENSION_HOST_PATH to your Live app, pointed at the Beta for live iteration, e.g. /Applications/Ableton Live 12 Beta.app.
2. In Live: Preferences → Extensions → enable Developer Mode (Live releases its managed host so the externally-launched one can connect).
3. Build and launch the host (leave it running):

   npm start

   npm start builds in dev mode and runs extensions-cli run, pointing storage/temp at ./.dev/ (git-ignored) so your token and catalog cache persist between runs.
4. Right-click an audio clip → Separate Stems with MVSEP.

Build & package

npm run build               # production bundle → dist/extension.js
npm run package             # build + package the installable → release/<name>-<version>.ablx
npm run package -- --reveal # same, then reveal the .ablx in Finder (macOS)

npm run package writes the installable to release/ (git-ignored), clearing any older .ablx first so there's only ever the current one. Install it by dropping the .ablx onto Live's Extensions preferences (with Developer Mode off).

Test

npm test           # unit tests (Vitest) for the SDK-independent modules
npm run typecheck  # type-check the extension

Behavior & limitations

• Arrangement clips render exactly what the clip plays (pre-FX, trimmed, warped) and place stems 1:1 at the original position. Faithful to Live's built-in stem separation.
• Session clips separate the clip's source file (no arrangement render is available). Unwarped clips get their region mirrored onto the stems; warped Session clips are best-effort: the placed region may not match what the clip played (surfaced in-app).
• Stems are placed unwarped (the Live API can't author warp markers), so they won't re-stretch if you change the project tempo later.
• No true Live group track (the SDK has no group-creation API), hence the ⌘G hint.
• Non-premium mvsep accounts allow one job at a time; v1 separates one clip per run.