Find a song your Pixel recognized earlier

Open the Now Playing app and tap History. It lists songs Now Playing recently identified. Search for the song, or use the date and time filters if you remember when you heard it. When you find it, swipe left on the entry or tap More to add it to Favorites. You can find it again under Favorites.

If the song is missing

History records recent identifications, so an absent entry does not tell you why the song is missing. Automatic recognition starts with the phone’s on-device library and may search the cloud if that library finds no match.

If the music is still playing, tap Now Playing in the app or Quick Settings to start a manual search. Manual search checks music playing now, so it cannot identify audio from an earlier moment after it has stopped.

For future songs, check Settings > Enable Now Playing in the app. If you recently downloaded the app, Google says you may have to wait up to 24 hours to use it.

Source: Google Pixel Phone Help. These are Google’s documented instructions; they were not tested on a Pixel.