Pandora iMessage App - Say it with Pandora — Send and receive songs in iMessage
Magic Playlist - Get the playlist of your dreams based on a song
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.
Spotalike - Spotify playlist with similar songs, according to Last.fm
Spotify - Map shows when two people play same song at same time
Playlist Machinery - Tools that help you create & organize your Spotify playlists