So I dismissed the instructions without reading them thoroughly. Everything was super confusing and it was unclear what up or down did, other than start playing different music.
It seems weird that up chooses a new artist and down chooses the next song. I heard a song I like, accidentally pressed down, and then up went, in an attempt to get back, but instead was sent to another artist. Super confusing.
The back button randomly changes artists. This is also super confusing. Couldn't you have a button for that?
When I click on one of the albums, the transition doesn't make it clear that it's now playing what you clicked on, and the previous list is now GONE. I assumed clicking would "select" the album. Also, once I've clicked an album, there's no way to get back.
And finally, my general feeling about the interface is that it's too focused on "power users", not being quick and easy to understand. I doubt this is something that needs really easy hotkeys, and if it does, it should be complimented with buttons that do the same things.
Don't let this feedback discourage you. I think you're solving a real problem, it's just hard to get past the UX. My advice would to to do some user testing. When you're building a super experimental UI, that isn't like anything else in existence, you probably want to verify that it doesn't completely confuse people.
tl;dr Do some user testing and you'll see most of these problems for yourself.