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