Copyright of The Song over the Screen
I think, Twitch or the owner of the song coulding put a small note over the live transmition telling viewers that they are the owner of he song. And the song also could be buying at Amazon or somewhere else clicking on the info. In my case Im an old Dj with more de 50 years and I use to play most 70 and 80 and sometimes my guests ask for the name of the song. If there is a link maybe they can be get interesed go out there to buy.