An app from Google called Sounds recently surfaced on the Play Store that, when installed on compatible phones, enables a collection of alarms, ringtones, and notification sounds previously only available for the Pixel. You'll also get the visualizations that go with them — those flowing gradients of soft, muted colors that show up on the display of a Pixel when, say, your alarm goes off in the mornings.
Naturally, you can't install Sounds on a Pixel, even though the screenshots on the Play Store listing are from a Pixel 3; should you try, you'll receive an error saying that it's already installed because, well, the sounds and visuals are already there.
Interestingly though, downloading Sounds on a compatible app yields no results for the time being. Google will be pushing a server-side update to the app later on that enables the Pixel sounds and visuals, but until then the app is basically just an empty shell with a button that doesn't do anything — this clearly isn't meant to be available just yet.