I'm planning to make a drum controller (something like arduino) for pc using a piezo transducer as sensor, some electronic circuit, keyboard PCB connected to usb and sampler for drums in pc. I found out that some people have similar plan, but they didn't finish it. So my plan may look like: I hit the piezo, signal will be amplified with OP amp, then I need something what basically connect two contact in keyboard (e.g. for letter "A") or just lower resistance between them under 40k with with the piezo signal. I used transistor as switch. Hope that you understand it. I designed scheme below, but it doesn´t working. Please help.