Barberpole rhythm and Mystery tune

Here's something that I think is interesting, if not directly tuning related.

There's a rhythmic effect that I like, a sort of rhythmic shepherd tone,
where a repeated section of music seems to speed up or slow down every time
it repeats, but after a while you realize the tempo isn't changing, or else
it would be extreme by now. I like this effect, but I don't know of many
examples outside of my own work. The file...

http://lumma.org/list/mystery.zip (48K)

...contains one of them. To my ear, it seems to slow down at each repeat.
I think this is because the change from 3 to 2 is sneeky, while the change
from 2 back to 3 is abrupt. How does it sound to you?

The first person to identify the origin of the tune wins a prize.

Carl