>In other words, each new song now has to be significantly different from what came before, so as to conform to our expectation of randomness. Which isn't really random at all.
I like to say "Random is blotchy". If we mean "uniformly randomly chosen with fully independent choices", smoothness is proof that it's not that sort of random.
This comes up surprisingly often. For instance, the mere presence of clusters of some non-communicable disease or something prove diddly. It must be shown that the clusters are unexpectedly large, not merely that they exist. Of course they exist. That's the default presumption.
That's the trouble with randomness. http://dilbert.com/strips/comic/2001-10-25/