4-pin-momentary button replacement with 2N2222A
The main IC in your Velleman kit is the HT8950, a voice-changer audio effects circuit, from Holtek. I would download the spec sheet and study that. In particular, you want to learn about those 4 control input pins (VIB, TGU, TGD, ROB). What kind of signal do they require? 
I think they may be "toggle" inputs. That means, you only need to send them a short pulse to activate or deactivate the effect.
BTW the 2N2222's base threshold is only 0.6 volts (like all BJTs). You need a series resistor to limit the current, like 10,000 ohms (brown-black-orange).