I was thinking of some ways to maybe pull off a funny senior prank. I decided that since the computers at my school had a free USB port on the side facing away from the monitor, this would be a perfect place to hide and/or power a pranking device. To me, the idea of the media center’s computers sputtering out video game theme songs whilst frantic librarians and students rushed to find the source seemed quite hilarious.
Unfortunately after completing my design I realized I could barely hear the music the piezo was playing! No one would even notice it if they weren’t in a completely quiet room.
A few months later, I was on adafruit.com when I read about “differential drive” for piezo elements. This method used two I/O pins to swat the voltage levels back and forth between high and low that allowed the Music USB to be twice as loud. Alas, school was already too close to ending to have enough time to pull off the prank.  (so I waited until freshman year of college)