Music experiments: perfect pitch

Last week I was busy doing something domestic, when I heard some clinking glass in the kitchen.  I peeked in to see what was going on, and saw this:

Thanks to Bill Nye the Science Guy, WonderGirl has been turning into a regular scientist.  I'm not complaining!  She was doing a pitch experiment that was seriously impressive and simple.  I grabbed the camera and started asking questions.

 To try this, you'll need:
2 glasses
a separate cup/pitcher of water
a metal utensil (she used a spoon)

Fill one glass halfway with water, then put less in the other glass.

 Tap on both glasses to hear the pitch of both.  Does the less full glass sound higher or lower than the other?  Then slowly fill the second glass, testing periodically by tapping, until both glasses are the same pitch.

 Then grab another spoon and start jamming out on both glasses.

Last step - wipe up the mess :)  What a fabulous, quick experiment!  Thanks, WG and Bill Nye!