Wonderful work. I do music and I was thinking it would be so cool to have each respective instrument section drop out of the song you're listening to when you lose it. You'd need a different file playing for each section, but just something to keep in mind if you take this further!
The tutorial boxes ended up losing me some sections by interrupting drags, maybe have them wait until the mouse isn't held down to come up. Great visual polish, you don't often get a lot of that.