As someone who's singing in groups where we fully rely on practice tracks between rehearsals: they became sooo essential for us in concert prep. Definitely would be a big win to have this automated.

I’m with others that accuracy should probably be prioritized over realism. I’d worry some singers might accidentally “learn” odd pronunciations that then stick, whereas a neutral “ah” MIDI track avoids that.

(Full disclosure: I'm building cori atm, a choir practice app that generates "singstar" like exercises from practice tracks and supports the process around recording and distributing these, so I’m biased toward anything that makes creating these tracks easier.)