This is better than I originally thought, but it's still a bit confusing. The Stems file spec (available via registration) is basically an MP4 container with so

This is better than I originally thought, but it's still a bit confusing. The Stems file spec (available via registration) is basically an MP4 container with some JSON metadata. This seems to have the usual donwsides of MP4 patents, but it's actually about as good as any standard a pro audio software company has released. Ideally, I'd have liked to have seen a completely open audio codec used for both encoding and container, but MP4 is a pretty safe bet for compatibility , and it's not really NI's fault that it has some patent issues. All in all, I could pedantically argue the "open" status, but I'll instead give credit where it's due, and give kudos to NI for releasing a pretty damn usable file format. I'm even happy that it's limited to 4 parts. For the purposes of live performance with DJ style gear, this is plenty. If a performer wants more parts then they're probably going to be creating some or all of those parts. Either way, they'll probably be using something more like Ableton rather than Traktor.