Why the issue with .wav's? At least Yamaha provide a large enough HD that using .wav's shouldn't be a problem, and you can swap out for a larger one, I would imagine.

Here you are, with presumably the best arranger on the planet (at least, that's what the fanboys will have you believe!), and you want to play crappy, lossy MP3's on it instead of nice pristine CD quality .wav files?

You can't bitch about compressed ROM waveforms on the one hand, and turn around and go 'What?! No MP3's?' on the other hand...

You can always convert your commercial karaoke tracks into .wav files, if that's what has got you all so worried.. Bet you wish you'd bought them on CD, now, instead of downloading them off of Limewire....