Google’s “Now playing” feature constantly listens to what’s going on in the background to show you what songs are playing. They claim this is done with a local database of song “fingerprints”. The feature does not show the microphone indicator because: “…Now Playing is protected by Android’s Private Compute Core…”

I’m not saying that other, non-google, app do this to my knowledge; but the fact that this is a thing is honestly a bit scary.

Edit: screenshot of the “Now Playing” feature