Ohhh, if I were the ornery type I'd drop the name of every earworm I can think of,
right here!
Near as I can tell though, my mask was sticking pretty much with the minuet from the
Grand Serenade for an Awful Lot of Winds.
Seriously though, thanks everybody for the suggestions (and the fun!). O-rings helped a lot, and pretty much took care of one source of leak. Now that the pillow leak is under control, I can tell that there is another leak from the ball-and-socket swivel where the two parts fit together. I haven't figured out how to hand that one yet, although I think I'll try taping the swivel joint to see how it does tonight. (I'll stay clear of the exhaust port!)
The first six weeks with this Opus mask were wonderful, but since it hasn't been mishandled in any way, either they aren't built to last, or I simply got a lemon. Time will tell.