What stems does StemRoller create from a song?

StemRoller splits a song into four stems — vocals, drums, bass, and everything else — and also produces a separate instrumental track that mixes all non-vocal stems into one file. This applies to any song you can find through its search bar, and the output is intended for uses like karaoke, vocal isolation, and drum or bass practice tracks.

The four stems StemRoller generates

According to the StemRoller site, typing a song name into the search bar causes the app to find the song online and separate it into these four parts:

The "everything else" stem is the catch-all for anything the model doesn't classify as vocals, drums, or bass — for example guitars, keyboards, strings, or synths.

The extra instrumental track

Alongside the four stems, StemRoller automatically creates an instrumental. This is described as all non-vocal stems mixed down into a single track. In practice that means vocals, drums, bass, and everything else are separated, and then the drums, bass, and everything-else parts are recombined without the vocals.

That instrumental is the file you'd use for karaoke or backing-track purposes, while the individual stems are what you'd use if you want to mute, replace, or process just one element.

What this means for common tasks

• Karaoke or instrumental version: use the auto-generated instrumental track, which already excludes vocals.
• Vocal track: use the vocals stem on its own.
• Drum or bass practice: use the drums or bass stem individually.
• Custom mixes: combine any subset of the four stems yourself.

How the separation works

StemRoller is built on Demucs, described on the site as Facebook's AI/machine learning research project. The site states StemRoller is totally free and open-source, and that it's available for download, with an optional donation link. If you run into issues or have questions, the site points to a Discord community for help.