I messed around with a custom keyboard st keyboard connected to some homemade drumpads, but I never got any good results. So I went out and bought this http://www.alesis.com/triggerio It's a trigger pad module that lets you connect virtually any type of pads, then it sends midi messages via midi or usb. I use it along with some quite cheap roland pads. I have never tried it along with my ST though but if the tracker accepts midi mesages this is the hardware to use, it works great and is very easy to setup/use :)
