Google rolled out a surprise update this week to the system Sounds the app on your Pixel phone. The update comes as Sounds 2.0 and no, you can not find it in your app tray. Instead, it is updated via Google Play to be available only from the notification and the ringtone sounds select. That's pretty good, though!
The previous audio selector from Google Pixel line was a default ringtone and notification sound selector. It was basically a list of available sounds. Now you have categories, a colorful user interface that moves around in weird ways I can not explain as you listen to each audio, and Google should be able to add it over time as they do with the wallpaper app. 1
The update to Sounds 2.0 should be available to almost anyone who owns a Pixel, Pixel 2 or Pixel 3 at this time.
Google Play Link