SoundGrail - SoundGrail Music App designed for pianists, guitarists, and DJs.
Spotify - Map shows when two people play same song at same time
keezy - A colorful soundboard. Play with music.
Playlist Machinery - Tools that help you create & organize your Spotify playlists
Figure - Propellerhead creates world-class software products and services that inspire music makers and provide the foundation for a worldwide creative musical community.
Magic Playlist - Get the playlist of your dreams based on a song