Quantity   Component name
1 × Rock Band Keytar
2 × XBee Series 1
2 × XBee adapter protects XBee from USB's 5V and has good buffering to prevent data loss
1 × FTDI Cable for talking to XBees
1 × Cheap USB-MIDI cable find 'em on Amazon, eBay for $6 or less
1 × 6N138 Optocoupler
1 × Hex Inverter for buffering
3 × 220 Ohm resistor
1 × 470 Ohm resistor
1 × 1 kOhm resistor
1 × LED Fiber Optics / Emitters
1 × USB type B jack
1 × 5-pin DIN jack