Here's an—in my opinion—almost exact equivalence: a font is a little program in a nearly-Turing-complete language. Nobody really cares what fonts end up on your computer. But if you create an image (e.g. an advertisement) that contains pixels manipulated by the font-program you ran on your own computer, then you have to pay to license that use of the font.
Within the realm of audio production, there's an even closer equivalence: soundfonts, which are also little nearly-Turing-complete programs. Playing a MIDI file "through" a soundfont? No problem. Putting that track on a CD and selling it? Nope, need to license the font.
Really, you could think of procedural music generation as a really complex and "stateful" soundfont program that has a nonlinear relationship with its input.
But in your examples derivative product depends on creative input which was put into original product. Music generating AI can be replaced by other AI created by different people but on the same principles so it produces similar music. Binaries produced by gcc don't bear GPL license and Adobe can not dictate license on pictures created in Photoshop.
> Binaries produced by gcc don't bear GPL license and Adobe can not dictate license on pictures created in Photoshop.
I don't think there's anything legally stopping either behavior; it's just that neither GNU nor Adobe are in a market position where anyone would put up with that sort of behavior.
Within the realm of audio production, there's an even closer equivalence: soundfonts, which are also little nearly-Turing-complete programs. Playing a MIDI file "through" a soundfont? No problem. Putting that track on a CD and selling it? Nope, need to license the font.
Really, you could think of procedural music generation as a really complex and "stateful" soundfont program that has a nonlinear relationship with its input.