While the official Native Instruments STEMS app is still to be released, developer Alexander Nowak has released a tool for Mac OS X that lets you create STEMS format music files now.
Here’s what he has to say about it:
So far it only runs on Mac and it’s still quite unstable if you do anything but what he says in the video. Some people said you have to be on the latest version of Java and control-click the .jar to make it work, this way it seems to work on all modern versions of OSX.
This version only covers importing the 4+1 tracks into the STEM file, but Nowak plans to include the compressing unit, custom artwork and artist information in the next versions.
It’s a free download (.zip), but is an early beta. The developer notes, ‘ don’t even know if it runs on any other computer but mine, let’s see, good luck. Please also read the README.txt cuz the app is still fragile af, if you do one thing wrong it won’t warn you, it will just fuck up on spot lol.”
If you want to give any feedback, contact the developer directly at mss.geoteach[at]gmail.com.