StemDeck

If you like StemDeck and find it useful, consider buying me a coffee ☕.

Paste a YouTube URL, get the audio split into stems (vocals / drums / bass / guitar / piano / other) and play them back in a DAW-style multitrack mixer. Mute, solo, mix, zoom the waveform, loop a region, and download individual stems or a custom mix.

Local-only, single-user. One Python process serves both the REST/SSE API and the static frontend.

What is this? StemDeck is meant to be an open, free, simplified alternative to commercial stem-splitter products like Moises, LALAL.AI, and similar tools. It runs entirely on your own machine, with no account, no quota, no upload, and no subscription. Source-available so you can read, fork, or self-host it. It is not trying to match those products feature-for-feature; it covers the basics well and stops there.

Honest comparison

| | StemDeck | Moises / LALAL.AI / similar | | --- | --- | --- | | Price | Free | Freemium or pay-per-use | | Hosting | Runs locally on your machine | Cloud, upload required | | Account / login | None | Required | | Stem model | Demucs htdemucs_6s (6 stems) | Proprietary, often higher quality | | Polish | Functional, hobby-grade UI | Polished apps (web + mobile) | | Extra features (pitch shift, chord detection, click track, lyrics, BPM tap, mobile apps, cloud library) | No | Yes | | Privacy | Audio never leaves your machine | Audio uploaded to a third party | | Source code | Available, modifiable | Closed |

If you need the polish, the mobile app, or the extra musician-facing tooling, the commercial products are a better fit and worth the money. If you mainly want stems for personal study and prefer to keep things local and free, StemDeck should be enough.

Features

• 6-stem separation via Demucs htdemucs_6s. Auto-detects the best Torch device (CUDA, MPS, CPU); on Apple Silicon you get ~3-5× speedup over CPU for free.
• DAW-style waveform editor. Min/max sample rendering across all stems with shared global normalization, zoom in / out / Fit (+ / − / Cmd-wheel), loop drag on the ruler, gold playhead overlay, and stem-aligned lanes.
• Stem subset extraction. Click stem chips on the import page to pick which stems to keep. Filter-chip semantics: clicking from "all selected" snaps to "only this one"; subsequent clicks add or remove. Selection persists in localStorage.
• "Original" backing track. When you pick a subset, the studio includes a 7th lane with the complement (full song minus the selected stems). Playing it alongside the isolated stems reconstructs the full mix without doubling, which is perfect for A/B reference.
• Downloadable selected mix. A single mix.wav of just the selected stems, summed via ffmpeg amix. Surfaces as the Download Mix button in the footer.
• Per-stem mixer. Volume fader, mute, solo, and "monitor" (solo-only) per stem. State is synced between the preview mixer and the stems sidebar.
• Live VU per stem.