To add to this, as a software engineer, while thinking through Smule's AutoRap app and the Shred Video app, I couldn't help but think that they could both probably benefit from a similar method for detecting (or synching with) beats, chorus, etc. Even though this sort of audio posterization (I'm not sure what it's really called) is not entirely novel, it's probably a reasonably tough problem to solve. If I had to guess, I'd guess that this aspect is what Smule's case is based on.
FTR: I hope Shred Video wins, because, based on the Business Insider article linked herein, Smith seems to be, IMHO, a huge bully.