In fact piezo materials are similar or identical to the composition of some ceramic capacitors, the
same class of titanate minerals are used which have very large dielectric constant and are ferro-electric,
meaning the mechnical distortion of the crystal lattice pushes charge across the crystal. So piezo elements
are perfectly serviceable ceramic capacitors in their own right, but engineered to bend easily - ceramic
capacitors made from these materials are "microphonic", so it you give them a sharp tap you'll see a
voltage spike from them - they are not used in audio circuits for this reason.