We created this iOS mobile app for a client who specializes in providing piano accompaniment tracks to individuals for auditions or educational purposes. The user has the option to choose between a subscription model or purchase individual tracks without a subscription and create playlists of the chosen content. In addition, he/she can change the key/tempo of the track and set rehearsal markers.
The challenge was that a song was not the root data item but broken into multiple tracks, and these tracks could be modified in several non-standard ways.
Many sessions with the client and developer resulted in a flow map that needed to be solid (and signed off) before we started working screen-to-screen.