In a party or any social gathering that requires music, Limelight allows the guests to construct the music with a voting system. Limelight gets its music from Spotify.
This was an app that I created during my time as an undergraduate. I have taken it off the App Store because I didn't feel like paying for the $100/yr Apple Store fee anymore or attempt to monetize the app. As of this date of commit, Spotify released a beta feature that supports collaborative playlists without voting. Any credentials or access keys from the repo's commit history won't work.