I should mention another demo I did for my physics of music classes
with a Helmholtz resonator. Take a "stubby" beer bottle and blow
over the hole to sound its resonant modes. I can (or could) get four
modes with a "cheater" bottle I made by grinding the far lip of the
stubby to a fairly sharp wedge. Even with my lousy flute embouchure
I could do this, while my students, provided with standard bottles,
could not. Usually I let them in on the secret. I'll probably never
get into the magician's union, and James C. Petrillo certainly never
wanted me.
Leigh
(Anyone who understands that last allusion should go take a nap.)