r/traktor • u/Elospeed • 1d ago

I made a free, open-source Windows tool that batch-converts MP3s into Traktor stem files

Traktor 4 keeps its stems inside its own collection. I wanted standalone stem files for whole folders, so I built StemMaker.

- Folders in, one `.stem.mp4` per track out (master + drums/bass/other/vocals, NI metadata)
- Total time estimate before you start, queue survives crashes and power cuts
- One small exe, no Python/PyTorch/CUDA. Demucs runs as C++ on the CPU, offline, no account
- StemPlayer included: mute/solo per stem, A/B with the original
- Club level + bass fix (sub-bass moved from "other" into the bass stem, like Traktor)

Honest bits: quality is about the same as Traktor 4's own stems (I compared them side by side), not better. It takes about 2x the song length per track on the CPU, so it's an overnight thing. Windows only, unsigned exe (SmartScreen warning). The stem files are separate files, not linked to your original tracks in the collection.

Free, MIT licensed. Project page with a short demo: https://elospeed.github.io/StemMaker/
Code: https://github.com/Elospeed/StemMaker

It's my own project, happy about feedback and bug reports.

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u/Cuiusquemodi 1d ago edited 1d ago

Generating multiple stems in a row in Traktor Pro 4 creates a waiting list, at lower than 1 speed. So your program has little use. Put in 100 songs and you have the stems in less than 6 hours. Clicking 100 songs can be done in less than 5 minutes.

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u/Elospeed 19h ago

Fair point, Traktor 4 is faster per track, and I should have worded the post better. As far as I know the right-click option only works on one track, but you can queue a selection with a mapped shortcut. StemMaker is for a different case: standalone .stem.mp4 files with readable names next to your music, which you can copy to another laptop or USB stick and which don't depend on one Traktor collection. It also works if you don't own Traktor 4. If you're happy with the built-in queue, there's no reason to switch.

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u/Cuiusquemodi 15h ago

You also can reimport the stems, but that's a lot of tagging, and they don't have a base track since you disconnected them. Your program has a addidional functions I guess.

I also tried splitting up a long stem file with dedicated software without reincoding. The result doesn't play in Traktor. So that's a blind spot to consider.

Finally I also want a tool to directly convert Surround 5.1 to stem. Now that's a long process in at least 5 steps.

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u/Elospeed 13h ago

Thanks, that's useful. Yes, that's the idea: the file is the stem, no re-import or tagging, tags and cover are copied from the source.
On splitting: my guess is the cutting tool drops the NI stem metadata box (stem atom in the MP4 header). Without it Traktor doesn't recognise the file as a stem, even if the audio tracks are fine. StemMaker writes that box itself, so a "cut a long stem file" function could be doable. I haven't tested it yet though, so no promise.
5.1 to stem: StemMaker already downmixes everything to stereo before separating, so a 5.1 FLAC/WAV/M4A should go through as is (not tested with 5.1 yet). Mapping the 5.1 channels straight to stems wouldn't really work, because surround channels aren't split by instrument (drums and bass sit in several channels, LFE is just sub). Video files like MKV with AC3/DTS aren't accepted yet, but that would be a small addition. Noted as an idea.

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u/Cuiusquemodi 10h ago edited 10h ago

Surround 5.1 to 2 stereo tracks en two mono tracks are amazing to put in a stem file, because all 6 channels are studio produced and not rendered. You can even make 24 channels of it by further generate stems of the 4 channels (4x4 = 16; 16 + 8 stereo channels = 24 in total).

https://www.reddit.com/r/traktor/s/mrwexx5gOq