Aren't you then saying that melody-ness is being conferred by the composer? That would make it extremely difficult to confirm that something is a melody or not

Aren't you then saying that melody-ness is being conferred by the composer? That would make it extremely difficult to confirm that something is a melody or not by observation alone (and thus likely impossible when determining whether other apes can come up with melodies). That said, I think the article is not using "random" in the literal sense but in the sense of "arbitrary", as in "novel" (rather than being simply a reiteration of a previously observed tune).