Re: i don't know a good title for this....
Philly's got it. The principle is more or less the same as playing 7/4 against 4/4 one time sig against another, and there will be a noticeable moment every 28 bars where it all lines up.
I've attached a brief MP3 of the tones 40, then 41, then both together. If you look at the waves in Audacity you'll see that compressing to MP3 distorts the square waves.