The incorporation of music into Twitch started from the bottom up, with some broadcasters playing music while streaming their game playing. “Over time, Twitch management became aware of this and so began doing some experiments and exploring whether music was a viable part of the platform.” However, getting the music side of things up and running wasn’t so simple. “Unfortunately, initially rights holders would not play ball at all with Twitch.”
Source: How Has Twitch Managed to Become a Go-To Music Platform During COVID?