Perhaps this is outside the scope of what you want the app to be, but...

I teach high school English. We will frequently create audio products like podcasts, speeches, Tedtalks, etc.

Traditionally, I would offer feedback in person while a student is drafting/editing their products - but with distance ed. that is somewhat more challenging.

The feature I would like is the ability to add an annotation to the audio track (either written or verbally) that is tagged to a specific moment/stretch of audio.

The ability to have creators add submissions to a shared folder would also help (such that I can rapidly click through and provide feedback on a large set of submissions).

Just spitballing, but maybe like genius.com but for private feedback on audio.