Spotify - Map shows when two people play same song at same time
SoundGrail - SoundGrail Music App designed for pianists, guitarists, and DJs.
Last.fm - The world's largest online music service. Listen online, find out more about your favourite artists, and get music recommendations, only at Last.fm
Figure - Propellerhead creates world-class software products and services that inspire music makers and provide the foundation for a worldwide creative musical community.
SoundCloud - Enjoy music & follow favourite artists
Splice - Music creation, collaboration, and sharing made simple.