At first glance, if you can scale your user base you COULD have artists/labels pay you to add songs to playlists (of course that fit) and charge flat fees for the promo playlistings.

Charge $1 / user and setup targeting at genre level for MVP and similar artist level at your later stage version.

So a label/artist says "we want people who like electronic", you have 150 people in the list. You charge the label/artist $150 to add their song to the playlists which you generate.