Tim is the founder of Pandora.com, and a musician. He started out wondering how a listener finds musicians, and realized that we all have a “genome” in our head for the music we love. Tim wondered how he could put the genome down and use it to suggest music that you might like. This was the start of the Music Genome Project, a massive taxonomy of music. Whether you are Tom Waits or Ella Fitzgerald, they can describe your voice along the same axis. The Music Genome Project uses 400 attributes to describe music.
The Music Genome Project has used specially trained musicians to describe and catalog half a million songs. On top of that data, they launched Pandora.com, which lets listeners create stations that fit their tastes in ways previously impossible. Pandora just reached 3.5 million users (not sure I got that number right) without any advertising.