Slate’s Farhad Manjoo explains how Shazam works. If you’ve never seen Shazam, check it out, you’ll be amazed. Its incarnation as an iPhone app is its most famous — I had no idea it started out as a dial-in service. Shazam fingerprints songs and then compares the fingerprints of submitted samples to their database. The service fingerprints “important” notes in a song, not sequences of notes. I wonder how long note sequences would need to be to constitute a unique fingerprint? It’s probably less than you think.