Grumpy_Mike:
Maybe a 20K to 100K would be a better compromise.
Is there any way to calculate this to a more exact number? It would be nice to be able to know what value of resistor for ## of piezos. The issue is that I might want to add more piezos in the future but changing resistors on a PCB would be difficult. Also, what works on a breadboard never works the same on a PCB (1Mohm was fine on a breadboard but on a PCB obviously it sucks) so it would be great to know what will work before soldering.