Hey there,
First and for most, I do these kind of circuits for pure fun, and I have no formal education in electrical engineering what so ever (I am actually a senior medical student) so please, bare with me, and try to keep it simple..

Recently, I have built a guitar controller from parts that were laying around in my house, and an xbox 360 controller.. and it works great, so I was thinking I could also build a custom Drum controller as well..

The main problem is that I need a sensor that senses vibrations and acts as a pushbutton that I can hook to my controller board.. hit the drums, close the switch momentarily.. here's what I've learned so far:

- a piezoelectric disk (such as the one in a buzzer) can be used a sensor for vibration as it generates high potential low current when deformed.
-you need a microcontroller (like most of the readily available drum kits and midi devices) to let the board know which is on and which is off.
-you need a pull down resistor to negate the "floating" state.

I can't use a microcontroller (strictly out of financial reasons) so I was wondering if there is a way to make this work without it, here's what I've tried :

-soldered 2 wires to the "signal" and "gnd" leads of one of the buttons on the xbox 360 controller pad
- extracted the disk from the buzzer, and connected the disk to the wires from the pad (directly) like so:
On board Signal lead ---------> Piezoelectric Ground lead
On board Ground lead --------> piezoelectric Voltage lead

-tried the board to see if a tap is registered as a button press, and found that every 10-15 taps registers as only 1 button press!

I think I need a capacitor to make sure that every single tap registers as button press, but I am currently a bit lost, and need to know if the idea is even sound and applicable (without the use of microcontrollers that is)..

Thanks, and sorry for the extra long question..

I made some rather embarrassing spelling mistakes, so I am pretty sorry about those.. it's not my native Language after all :D