Create .stem.m4a from your own stems
Vibe coded
This utility was built quickly with AI assistance and only lightly reviewed. It packs files with the same encoder and packer that NUO-STEMS uses for its own stems, but check the result in Traktor before you rely on it in a set. See why it's vibe coded.
This utility packs a master track and four stems that you already have into a Traktor .stem.m4a file. No stem separation is involved: your files are used exactly as they are.
Use it for stems from a producer's stem pack, exports from your DAW, or stems made with other separation software.
What you need
- A master (the full track) and up to four stems: drums, bass, other (melody) and vocals.
- WAV, FLAC, AIFF or ALAC (
.m4a) files. MP3 and AAC aren't accepted: lossy encoders add silence at the start and end of a file, so their length can't be compared to the sample. - Exactly the same length in samples and the same sample rate for all files. The utility checks this before it creates anything.
Mono files are accepted and duplicated to both channels. If a track has no such stem (for example, no vocals in an instrumental), you can fill that slot with silence of the same length as the master.
How to use
- Open NUO-STEMS 4 and go to Utilities.
- Choose Create .stem.m4a from your own stems.
- Drag the master and its stems onto the page, or click Add files…. Files are put into slots by their names (see below). Files the app can't place are listed in a warning above the table; drag a file onto a row to put it in that slot.
- Check the table. Each file shows its format, sample rate, length and number of samples. When a stem doesn't match the master, its sample count turns red and Diff shows the difference, for example
+1,024. - Check Save as (taken from the master's file name), Folder (the master's folder unless you change it) and Format (AAC 320, AAC 256 or ALAC, preset from Settings).
- Click Create .stem.m4a. The file appears in the Created list under the button with a Show in Finder (or Show in Explorer) link, and the slots are cleared for the next track.
To do several tracks, repeat steps 3–6: the folder and format you chose are kept until you close NUO-STEMS.
How files are sorted into slots
The utility looks for these words in file names:
| Slot | Words in the file name |
|---|---|
| Drums | drum, drums, perc, percussion |
| Bass | bass, bassline |
| Other | other, melody, melodic, synth, keys, chords |
| Vocals | vocal, vocals, vox, voice, acapella |
| Master | master, mix, mixdown, original, full |
A file without any of these words becomes the master when it's the only such file, or when the stem file names start with its name (for example Night Drive.wav next to Night Drive - Drums.wav).
"Instrumental" files aren't put into Other: an instrumental usually contains drums and bass too. Use ⋯ > Move to on a row to move a file to another slot.
What ends up in the file
- The master and the four stems, encoded with the format you selected.
- Tags and cover art copied from the master file.
- Stem names and colors from Settings > Traktor Pro > STEMS Colors.
Your original files are not changed.
Why it's vibe coded
I added this utility because users asked for it, not because I think it's the best way to make stems. So it only got a quick, AI-assisted implementation.
Stem Creator is the better tool for your own stems
For packing stems you already have, Native Instruments' free Stem Creator app remains the better tool. The main reason is the "compressor" & "limiter" in Stem Creator. It looks like some VST magic that NI built into Stem Creator to provide real-time feedback. I'm not familiar with this technology, so your best luck remains with Stem Creator 🙂
If Stem Creator doesn't work on a recent version of macOS, here is the fix: link
Generated stems are usually the better choice
Even when you have the original stems, I believe stems generated by NUO-STEMS are usually the better choice for DJing:
- Consistency. Every track in your library gets stems made the same way, so you know what to expect from each stem when you mix.
- Time. Generating stems from the original track takes one click. Collecting, naming and lining up the original stems of every track takes much longer.
- The stems add up to the original. With Sum of Stems = Original Mix, NUO-STEMS makes sure that the four stems played together sound exactly like the original track. Stems exported from a DAW often don't: processing on the master bus, effect returns and sidechaining usually aren't part of any single stem.
Original stems aren't bad. If you have them and want to use them, this utility is here for that.