tonestro - Practice & improve on your wind instrument while having fun
Magic Playlist - Get the playlist of your dreams based on a song
Piano2Notes - Piano2Notes is a web application and mobile that transcribes your piano tune into a digital word document.
Spotalike - Spotify playlist with similar songs, according to Last.fm
Melodics - Melodics is a desktop app that teaches you to play MIDI keyboards, pad controllers, and drums.
Spotify - Map shows when two people play same song at same time