Automatic Stem Separation

FreeMix can automatically split a track into its individual stems on upload. Upload a full mix, turn on stem generation, and FreeMix separates it into four parts — drums, bass, vocals, and other (everything that isn’t one of the first three) — that you can play, download, remix, and sell like any other stems.

Separation runs on FreeMix’s own infrastructure. Your audio isn’t sent to a third-party service.

You can upload your own stems

You can of course upload your own stems if you have them and that is the preferred way to provide stems for your tracks as they are coming directly from your source material. You can even upload your stems and let FreeMix generate stems during the same upload. There is a limit of 12 stems per upload, so you can’t upload more than 12 stems in total.

Why would I use the stem separation feature?

There are several reasons to use the stem separation feature:

• You are uploading a track or remix without stems
• You want to check out the automatic stem separation feature
• You want to use the stem separation feature to augment the stems you already have

Any of these are valid use cases. In fact, some of the “limiting” features of the automatic stem separation feature can be used creatively. For example, the “other” stem often pulls out interesting material in a way that dedicated source stems would not.

Separation quality

FreeMix separation is built on Demucs, a well-regarded open-source source-separation project and currently the most accurate separation model available.

If you choose to use the automatic stem separation feature, there’s nothing to configure — everything is automatic. You don’t pick a model — FreeMix runs the best separation your plan includes:

• Free — standard-quality separation.
• Pro, Plus, and Studio — the highest-quality separation FreeMix offers. Cleaner results with fewer artifacts, most audible on dense mixes and on the “other” stem.

What to expect from the quality

Automatic stem separation is very good (and getting better all the time), but it isn’t perfect — no separation model is. A few honest expectations:

• Drums, bass, and vocals separate cleanly on most material.
• The “other” stem is a catch-all for everything that isn’t drums, bass, or vocals — synths, guitars, keys, pads, effects. Because it holds the most variety, it’s usually where any bleed or artifacts show up.
• Dense or heavily-processed mixes are harder to separate than sparse ones. Results vary with the source.

If you already have true isolated stems, uploading them directly will always beat machine-generated separation as separation reconstructs stems from a finished mix, which is a fundamentally harder problem than exporting them from already-separated source tracks.

More stem types are coming

Today’s separation produces four stems. We’re working on models for more specialized types — synth, keys, guitar, and more. If you’d like to help make that happen, see Stems & AI training.

Separation limits by plan

Each plan includes a number of separations per month:

• Free — 3 separations per month.
• Pro — 10 separations per month.
• Plus — 25 separations per month.
• Studio — unlimited, within fair use.

“Separations” are the amount of times you’ve uploaded a track and let FreeMix split it into stems.

Your allowance resets at the start of each calendar month. See the plans page in the app if you need to upgrade or downgrade.

If you reach your monthly limit, you can still publish your track — the stems just won’t be generated automatically until your allowance resets or you upgrade. You can also upload stems directly at any time, on any plan, with no limit.

Consenting to help improve separation

When your upload includes generated stems, you’ll see an optional checkbox asking whether FreeMix can use those stems to help train its own separation models. It’s entirely optional and off by default. Full details are on the Stems & AI training page.