Most "which is better" answers repeat marketing. We ship both engines in one browser tool, run them on the same songs daily, and can tell you exactly where each wins — and why the difference exists.
Try both engines in your browser →
Spleeter for speed anywhere, Demucs 4-stem on WebGPU. Nothing uploads. Free to try.
Two models, two generations of thinking
Both networks do the same job — pull a song apart into vocals and accompaniment — but they look at the problem differently, and that difference explains everything about their results.
- Spleeter (Deezer, 2019) works like a picture editor. It converts the song into a spectrogram — a snapshot of which frequencies sound at which moments — and a compact network paints a mask over it: this energy is voice, that is everything else. Fast and light, because masking a picture is cheap.
- Demucs (Meta, evolving through 2022's htdemucs) works more like a musician re-performing the song. It processes the actual audio waveform through a deep encoder-decoder, modeling how each instrument evolves over time rather than judging frequencies frame by frame. Heavier — much heavier — and that's where its quality comes from.
Where you actually hear the difference
On a clean mix with a dry lead vocal, both produce very usable stems — many listeners won't pick a favorite blind. The gap opens under stress:
- Dense, loud mixes. Spleeter's mask tends to leave ghostly vocal residue in the instrumental and take some cymbal shimmer with the vocal. Demucs keeps the sides cleaner.
- Reverb-heavy vocals. Echo smears the vocal across time — a frame-by-frame mask smears its guess with it. Demucs' longer view of the audio tracks that trail far better.
- Fasts, transients, drums. In 4-stem mode, Demucs' drum separation is decisively more musical — hi-hats stay hi-hats instead of turning into artifacts.
Speed, weight, and what it costs to run
Spleeter (2-stem) — vocals + instrumental · runs on any CPU, phones included · fast on any laptop · songs up to ~30 minutes · usable on hard mixes, with some artifacts
Demucs (htdemucs, 4-stem) — vocals, drums, bass, other · wants a GPU (WebGPU in Chrome/Edge) · heavier, GPU does the lifting · songs up to ~8 minutes · clearly cleaner on hard mixes
So which should you use?
The honest answer is a decision tree, not a winner:
- Quick job, long file, any device — Spleeter. A 20-minute mix for a background track doesn't need (and can't run) Demucs.
- Karaoke night, casual covers — Spleeter at default settings is usually indistinguishable in the room, over speakers, with people singing.
- Remix or sampling, vocals front and center — Demucs. Every artifact you don't remove now is one you EQ around later.
- Testing if a song "can" be separated at all — Spleeter first for the shape of the result, Demucs for the keepable version.
Why we ship both instead of picking one
Single-engine tools make you fit the job to the model. The splitter we build puts both behind one drop-in, running entirely in your browser — Spleeter on any CPU, Demucs on WebGPU-capable machines — and both stems come out of a single pass either way. Because everything runs locally, you can A/B the engines on the same song as many times as you like, with unreleased material never leaving your disk.
What no stem-splitter can do
- Recover a vocal that was mixed into a single bounced file with full-band distortion — separation estimates; it doesn't un-mix physics.
- Beat stems delivered by the original studio. For release-grade work, cleared acapellas still win; for creative work, practice and remixing, modern separation is genuinely good.
Try both engines in your browser →
Spleeter for speed anywhere, Demucs 4-stem on WebGPU. Nothing uploads. Free to try.
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