It will eventually be sorted out in the contracts whereby the games get licences for whatever content: music performed in-game is 'part of the experience' etc.

It will eventually be sorted out in the contracts whereby the games get licences for whatever content: music performed in-game is 'part of the experience' etc. and/or because they are playing a game with the music artists will claim that it's an original work in it's totality. Twitch already has mostly DRM aware content creators - I hear them talking about 'rights' quite a lot in their streams.