When you say you want to emulate a piezo, do you mean you want to only deal with a limited range of frequencies (like a piezo)... you can do this by filtering data through a HPF. This sill give that thinner sound. No need to modify the samples (that would akin to modifying the strings and body of your classical guitar... you simply want to use FILTERs and EFFECTs to process the sound. Not knowing what YOU consider a piezo type sound _ you will need to experiment.
But piezo technology is a kind of lo-fi technology, you can FILTER the Elements to get the results you are looking for.