DMCA
TWITCH SHOULD BE REACHING OUT TO ARTISTS AND GETTING APPROVAL FOR ENTIRE PLATFORM!!! Many many many artists would love to be able to have their music played on as many streams as possible. After all, it's FREE MARKETING!! Twitch should work with these labels who own the rights to make these decisions over the artist, and bring music back to streams. Artists get free marketing, labels make more off of that as ewell as the artists, and viewers and streamers alike get a much more enjoyable product that can also lead them to music they love that they might've never found otherwise.
THIS IS AN ABSOLUTE TRAVESTY TO BOTH THE MUSIC AND THE STREAMING INDUSTRIES.

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VirtualNightclub commented
A lot of recording artists are signed to record labels, so they don't have the authority to clear the use of the sound recordings. Indie and other unsigned artists can conceivably grant such clearance but that doesn't help the majority of streamers that wish to incorporate mainstream music into their shows. What we ultimately need is a statutory license for hobbyist online broadcasters.