Passage Player

Displays scrollable panoramic waveform of any song in the user’s library, allowing the user to set visual breakpoints in order to loop playback of various passages. Musicians can focus on a particular passge for practice or close analysis. Users can also control playback speed and pitch, and can record themselves for A|B comparisons which contrast their own playing against that of the professionals.

I'm not only the developer of this app, but also a user. :)