Spotify today unveiled Serendipity, an online map that displays a live stream of coordinates whenever two users play the same song at the same time. Serendipity is accurate to one tenth of a second, Spotify says. The site isnt particularly useful, but is a fantastic visualization of how music spreads — and of the reach of Spotifys user base. Serendipity was built by Kyle McDonald, a Brooklyn-based digital artist who recently became Spotifys first artist in residence. The company, which is well known for its frequent hackathons, hack days, and jam sessions, largely gave McDonald the key to its data castle.