I made a xylophone that uses an Arduino Mega to detect when a note is struck, and generate MIDI output. This project is wondeful because I essentially made a xylophone, a drumkit, and any other MIDI controlled sound instrument, with one tool. The following steps will outline what I used to make this xylophone.
Step 1: You will need...
(x1) Arduino Mega 2560 (Radioshack #276-127)
(x12) Piezo Element (Radioshack #273-073)
(x12) 1M Ohm resistors (Radioshack #271-1356)
(x1) Single Core wire (Radioshack #278-1221)
(x1) Printed Circuit Board (Radioshack #276-170)
(x1) USB 2.0 Cord (Radioshack #26-714)
(misc) Electrical Tape (Radioshack #64-2373)
(misc) Heat shrink (Radioshack #55048444)
The housing for the xylophone was easy to build. I used:
1/8" acrylic sheeting
1/4" vinyl tubing
1 1/2" long machine screws.
2" masking tape
small flat head screw driver