> When a copy was finished (which could take some time), the program helpfully played a little "boing" sound.

And how that "boing" sound worked is interesting in itself. It's one of the few uses of Paula's "attached" mode, where the output of one sound channel is used to modulate the volume or pitch of another.

I put the full source code of the boing sound here: https://news.ycombinator.com/item?id=48174583