This is a genius idea. Using an already-existing and well-performing image model, and just encoding input/output as a spectrogram... It's elegant, it's obvious in retrospective, it's just pure genius. I can't wait to hear some serious AI music-making a few years from now.
As someone who loves making music and loves listening to music made by other humans with intention, it just makes me sad. Sure, AI can do lots of things well. But would you rather live in a world where humans get to do things they love (and are able to afford a comfortable life while doing so) or a world where machines do the things humans love and humans are relegated to the remaining tasks that machines happened to…
I think that kind of attitude is defeatist - it's implying that humans will be stopped from making music if AI learns how to do it too. I don't think that will happen. Humans will continue making music, as they always have. When Kraftwerk started using computers to make music back in the 70s, people were also scared of what that will do to musicians. To be fair, live music has died out a bit (in a sense that there aren't that many god-on-earth-level rockstars), but it's still out there, people are performing, and others who want to listen can go and listen.
Maybe consumers will start consuming more and more AI music, instead of human music [0], but the worst thing that can happen is that music will no longer be a profitable activity. But then again, today's music industry already has some elements of the automation - washed-out rhythms, sexual thematics over and over again, re-hashing same old songs in different packages... So nothing's gonna change in the grand scheme of things.