I'm currently working on something similar called MyJam, which lets you collaboratively build playlists and vote for the favorite songs which then rise to the top of the queue. We won Startup Weekend Ottawa! Check it out here: http://myjam.co/
Side comment: There is a site called https://www.thisismyjam.com/ might get confusing, not sure who was first though. It's pretty hard finding a unique name in this space, took me AGES to come up with Playlistful.