It's a patched version of YouTube Music app with the ReVanced patches for the YouTube Music package.

YouTube Music is a new music app that allows you to easily find what you’re looking for and discover new music. Get playlists and recommendations served to you based on your context, tastes, and what’s trending around you.
A new music streaming service from YouTube
● This is a completely reimagined music service with official releases from your favorite artists.
Find the music you want
● Easily find the albums, singles, live performances, covers, and remixes you’re looking for.
● Don’t know a song’s name? Just search for the lyrics or describe it.
Discover new music
● Get music recommendations based on taste, location, and time of day.
● Use “The Hotlist” to keep up with what’s trending.
Uninterrupted listening with Music Premium
● Listen ad-free
● Don’t worry about your music stopping when you lock your screen or use other apps.
● Download your favorites or let us do it for you by enabling Offline Mixtape.
Get one free month of Music Premium to listen ad-free, offline, and with your screen locked, then pay just $9.99 a month. Existing YouTube Red or Google Play Music members and users of either service who have already received a 30 day trial are not eligible. Monthly charges auto-renew for Music Premium membership outside of trial periods.