Pandora iMessage App - Say it with Pandora — Send and receive songs in iMessage
Slackbox - Spotify playlist collaboration through Slack
YouTube Music - YouTube Music is a streaming app primarily designed for Android and iOS mobile devices. The app lets individuals search for music from their favorite artists, enjoy playlists, and access 30 million musical tracks.
Partyhero - Pass your friends the aux!
Spotify - Map shows when two people play same song at same time
Songmash - Create playlists with music that you and your friends love