YouTube Music for Android gains new streaming and download quality controls2
Audio quality on mobile network” or “Audio quality on Wi-Fi.” Each of these new settings have four options: Low, Normal, High, and Always High.
There are also some new download quality controls available in the Downloads menu. You'll see a new “Audio quality” option that offers further adjustments like Low, Normal, and High. In addition, a “Video quality” should enable users to set the streaming service to only store audio.
The official changelog in the Google Play Store hasn't been updated to reflect the new changes, but they're probably rolled out in waves, so make sure you have the latest version of YouTube Music.