Edited If the neural network gets good enough that no significant work is required for the final product then I imagine you could change some pixels in the out

Edited If the neural network gets good enough that no significant work is required for the final product then I imagine you could change some pixels in the output and call it a "touch up". We're not there yet of course but ultimately how much effort does a touch up require to warrant a copyright? Is the touch up creative? Fixing blurry faces/hands seems like replacing a rusty pipe with a new one. For the musical piece, copyright probably expired or has no one to defend it today. At least with performance art, the effort of your derived work is easier to gauge. Your musical abilities and voice are unique to you and what, I think, is being copyrighted. You don't normally claim total ownership of the covered piece. Sam Smith got sued a couple times for his work (notes, not lyrics) being too close to others in what he claimed were original pieces.