Rolando Fuentes made a pretty cool MIDI e-drumset.
The brain of the drum pad is made using a Teensy-LC and 2 multiplexers. You can use Garage Band, or almost any other music program to play your new drum set.
The drum pad is made using velostat and a matrix of copper tape.
The code for the project as well as detailed instructions can be found on this Instructables page.