Already done. It's called Torrent Streaming and lets you stream-on-demand anything that exists as a torrent without having to torrent anything yourself.

A client that can stream these Spotify torrents with an interface that works like Spotify (low bar, I know) will be awesome, but also including a database to match songs to artists so users can send money directly to the artists they listen to will make it revolutionary.

When copyright dies so rich conglomerates can make money by monetizing out toys and collectibles and theme parks from smaller creators content without paying a dime back to them? Copyright is beneficial. Copyright is good. It needs reform, yes, but don't mistake that with the concept being bad.