I just joined your Testflight. Here are some notes/observations:
- when playing the songs which are presented to identify what music I like, when I tab an other button while music is still playing, the new music is playing, but the old button does stay at the "pause" sign and does not switch back to "play" sign
- I really do not like to sign up to anything without testing it first, so I consider that a bad user experience
- when signing up and being asked for a password, you do not integrate with iOS password management. You really should do that. There are videos from Apple WWDC which explain how to do that.
- when "take the tour" and going through the questionnaire I ended up with "no results", that should of course change :- )
- your videos are all sourced from Youtube? I think it would be helpful when focusing on videos which show the hand movements because the user would need to see that to judge difficulty level, no? (At least this is what I use videos for)
- it would be really great to have controls around the video to skip forward/backward for e.g. 15 seconds. Hard to go through a video fast.
- you do not seem to be linking to any videos which show how to learn/practice a song. Any reason? That would be helpful I think.
It would probably be a good idea to ask the user which pieces he has played and then suggest different pieces which are at the same or a higher level of difficulty?
You plan to show scores from public domain only? Or also integrate with Musicnotes or some other marketplace for sheet music?
In any case, a piano music discovery app is a good idea, I think!