Split any song into vocals, drums, bass and more. Mute, solo, change tempo and key, export. On your Mac, no subscription.
Stems does what Moises and LALAL.AI charge $14 to $20 a month for. It runs Meta's Demucs (Hybrid Transformer) on your Mac's GPU through MLX, so a 4-minute song separates in about 10 seconds and never leaves your computer.
Table of contents
- Four or six stems: vocals, drums, bass, other, plus guitar and piano with the 6-stem model
- Mixer: per-stem volume, mute and solo, all stems sample-locked while you play
- Karaoke in one click, acapella in one click
- Tempo and key: slow a solo down to 50% or shift the key up to an octave, in real time
- Export all stems as 24-bit WAV, or any mix (karaoke, drums only, whatever you have soloed)
- Private: models download once from Hugging Face, then everything runs offline
Signed with a Developer ID and notarized by Apple, so it opens like any other Mac app.
Download Stems.zip from the latest release, unzip, move Stems.app to Applications.
Requires macOS 14 Sonoma or newer on Apple silicon.
- Drop a song on the window (MP3, M4A, WAV, FLAC, AIFF, or a video).
- Wait for the progress bar. The first run downloads the model.
- Mute the vocals for karaoke, solo the bass to learn it, slow it down, shift the key.
- Export the stems or the current mix.
| Model | Stems | Quality | Speed on M1 Pro, 3 min song |
|---|---|---|---|
| Standard (htdemucs) | 4 | good | ~9 s |
| Fine-tuned (htdemucs_ft) | 4 | best | ~60 s |
| 6 stems (htdemucs_6s) | 6 | good | ~10 s |
Pick the model on the start screen before dropping a song.
How good is the separation? Demucs is the model the paid services are built on. Vocals and drums are clean; bass and "other" can carry some bleed on dense mixes. The fine-tuned model is noticeably better on vocals.
Can I use the stems commercially? Demucs and its weights are MIT licensed. What you do with someone else's song is between you and the rights holder.
Does it need the internet? Only for the first model download (about 80 MB for Standard).
xcodebuild -downloadComponent MetalToolchain # once, needed to compile MLX shaders
git clone https://github.com/Dunebru/stems.git && cd stems
swift test
scripts/build-app.sh # dist/Stems.app and dist/Stems.zipStems depends on demucs-mlx-swift (MIT) and mlx-swift.
MIT © dunebru
- Demucs by Meta, MIT
- demucs-mlx-swift for the MLX port