As a musician I was prepared to roll my eyes at this article but it's really good.

When I was a kid I would play with Music Construction Set on my Apple ][, "painting" lots of random notes into one or two bars and then putting repeat signs around then. What sounded totally random and annoying at first became kind of catchy once you listened to it eight times in a row.

The composer that I really admire for unabashedly using repetition before the Minimalists really took off with it is Olivier Messiaen (the Turangalîla Symphony has lots of great examples). Classical music is historically largely about continual transformation, and he was unafraid to just cut and paste big sections. It worked magnificently.