pandora re-opened

As a follow-up to a previous post I found this Inside The Net podcast on the Pandora music recommendation system. In the interview Tim Westergren, from Pandora, gives a few facts and figures on the system:

• There are 400 aspects in their taxonomy. And, for example, the vocal aspect includes the amount of vibrato, the vocal range and the "twiddlyness" (my words).
• To categorise music they employ people with music degrees and provide 40 hours of training on the taxonomy.
• It takes between 20 and 30 minutes to describe a song.
• They add 7000-8000 songs per month and, in total, describe around 15000 artists with 100,000s songs. In contrast there are typically 50,000 new albums per year in the US.

He thinks that playlists are what music is all about now and comments on how the most popular recommender systems up to now have tended to use collaborative filtering (e.g. other people that like this also like...). The flaws with this are that you can be stuck with bad choices from the past (or choices by your partner or presents or whatever) and that it is generally a popularity contest and is therefore not good at recommending unknown artists. Obviously Pandora has the same problem because they can only rate a limited amount of content though Tim mentions that they employ a couple of people who look for new bands to include - maybe in the future you won't need a record deal, just a playlist deal.