You're at a coffee shop. A song comes on. It's right on the tip of your tongue. You pull out your phone, tap a button, and it tells you what it is in a few seconds.

How does a phone listen to a few seconds of music through a noisy room and instantly match it against millions of songs?

Your first instinct might be that the phone is listening to the melody or recognizing the lyrics. It's neither of those. What it's actually doing is far more clever.