I’ll admit to not being the world’s biggest piezo pickup fan as far as the actual tone is concerned. They don’t sound enough like an acoustic to serve that purpose, and they don’t sound good at all when approached as like a traditional electric. But the science behind them? That’s some dark sorcery that I can get behind.
Seymour Duncan’s blog posted this great breakdown of the history and science behind piezos. It’s some seriously detailed and nerdy stuff. Head over and give it a read if you want to get a much better grasp for how they work, and why they’re such a love it/hate it kind of sound.