There are a number of web pages that attempt to explain in detail how Shazam succeeds in identifying what I'm listening to. Perhaps the most readably non-technical of these is by Farhad Manjoo in Slate from 2009. As far as "non-technical" goes, his is a good explanation, the gist of which is summed up in one paragraph:
First, a short explanation of how Shazam works. The company has a library of more than 8 million songs, and it has devised a technique to break down each track into a simple numeric signature—a code that is unique to each track. "The main thing here is creating a 'fingerprint' of each performance," says Andrew Fisher, Shazam's CEO. When you hold your phone up to a song you'd like to ID, Shazam turns your clip into a signature using the same method. Then it's just a matter of pattern-matching—Shazam searches its library for the code it created from your clip; when it finds that bit, it knows it's found your song.On the other hand, "simple numeric signature" and "pattern-matching" seem a bit too non-technical. That much I could have figured out by myself. I do, however, identify with Manjoo's appreciation of the app:
Other than playing video games, it's the most useful thing you can do on your phone.A considerably fuller explanation of how Shazam works can be found in a paper - An Industrial-Strength Audio Search Algorithm - by Avery Li-Chun Wang, one of the apps' founders, that Manjoo refers to. That paper is definitely too detailed for me, but if for some reason someone finds it not detailed enough, last year Christophe Kalenzaga posted a lengthy, and totally beyond my ability to understand, explanation of how the app works. No, I didn't read the entire paper. Considering that this was a very recent explanation, the absence of any mention of GPS answered, by default, a question I've asked. I've wondered whether, in order to hasten the identification process, Shazam might use my geo-location to scan the various radio stations I might receive and give priority to checking whether what I'm trying to identify is being broadcast at that time in my vicinity. It sounds like a workable idea, but apparently Shazam doesn't need to do this.
Any sufficiently advanced technology is indistinguishable from magicnot only was he right, he'd also given me all the explanation of Shazam that I really need.