This looks really cool, and it'll be interesting to see how artists and producers react. Presumably the tracks need to be mixed for the format with dedicated vocal track. Although it's possible to isolate vocals some of the time from mixes, using stereo separation (the vocals are often the only component that is 100% center mixed), filtering, and even AI techniques ... none are perfect.

I wonder if this will have the real killer feature of professional karaoke ... the ability to transpose the song into a more convenient key for the singer. Apple have had this capability in Logic Pro's pitch shift and it's pretty good even on polyphonic music. Some Karaoke platforms use midi and midi-like formats and synthesize the instruments to do it, but I'd be surprised to see that here.