[pfarrell]

IIRC, it's uses a Fast Fourier Transform of the time delay between high notes in the song to generate a series of "hashes" that are stored a db. Those ids can be calculated locally on the phone and then its a simple db lookup to retrieve potential hits. When Shazam adds a song to the db, they compute a series of "hashes" so you can identify at any point in the tune.

[synaesthesisx]

Wow, that's fascinating! I just ended up down the rabbit hole reading Avery Wang's "An Industrial-Strength Audio Search Algorithm" (linked in this thread) - it's such a cool way of "fingerprinting" pieces of music data.

[pfarrell]

My original comment was from memory of reading a post about how it worked a few years ago. Looking at what you read, I think the gist of what said is right, though it seems they use a different algorithm than FFT.

Totally agree though. It is something that opened my mind to thinking of a way to solve that problem in a way that actually works. Shazam definitely looked like magic the first time I saw it work.