Shazam is the closest thing we have to witchcraft. I'm sure plenty of HNers will chime in with "well acktually..." type comments about how they could write it in their basement in a weekend, but to do what it does, as quickly as it does, on the ridiculously enormous library of music that it does is really something special.
I agree with you, and I work in music audio signal processing. Shazam was founded in 1999-2000 ish and was live by 2002, longer ago than many people realise. The fingerprinting method they used was a novel one, and they successfully deployed it in a couple of years, with a database of two million tracks, in a system that could be used by dialling a number from any phone. It's an extraordinary and rare example of taki…
Would really be interested if someone has tried other approaches and can comment.