Some potential ideas - pay per listen, local cache - embedded lyrics, photos - extra sound bytes (exclusive to track owners) - optional videos - asynchronous Comms with the band: FAQs. News, interviews, etc

There are many things you can do that link purchased content with other content. Adding lyrics that appear in realtime would also be handy.

My ideas are now patented. Pay me 5% of all future sales please... Isn't that how patents work? State the obvious and rake in cash for doing very little?