You're probably aware that Google is having an event in just a little bit. We've heard plenty of rumors about what will be announced, including one suggesting that Google is planning an always-on music identification feature for the new Pixels. That's looking very much confirmed right now, thanks to a new listing in the Play Store called Pixel Ambient Services.
The app description isn't very helpful, saying only "Pixel Ambient Services provides features based on local context for Pixel devices." Okay, but the screenshots are a bit more useful. This app appears to enable local song identification, which plugs into ambient display. According to the settings screen, the Now Playing feature recognizes music playing in the background and identifies the song. It doesn't need to send any data to Google in order to do this. You just get a little popup on the lock screen and ambient display.
Pixel Ambient Services is currently incompatible with all devices, so it might only be for the new Pixels. Whatever Google's plans for this app at launch, it's possible it could be updated to support more "local context" features on the Pixels later. Keep your eyes peeled at the Google event for the new ambient features.