Way before apps were even a thing, around 2002-2004, I lived in the UK and shazam worked as calling service: you'd call 2580 (top to bottom on the center column of a phone numpad), it would listen for 30s, then would hang up and send you an sms with the name of the song. IIRC it would charge you something like 50p if it found a result.
One thing about load average on Linux which I never really understood was the inclusion of processes waiting for I/O, I never really got a satisfying explantation until I bumped into this post a few years ago: https://www.brendangregg.com/blog/2017-08-08/linux-load-aver...
It really felt like pure magic!