Heartbeat - Listen to music with your friends together, on Spotify
Plug - Lightweight OSX player for Hype Machine
Liyo - Stream your favorite music live with friends 🎶
Rocketgraph - Rocketgraph is an open-source drop in replacement to Firebase, except it's much better.
Festify - Festify is a free Spotify-powered app that lets your guests choose which music should be played...
Muru Music - Personalised playlists within seconds.