In order to build a VGM player for Sega Genesis, I need to send two 8-bit values at the same time. 1 byte for PSG. 1 byte for YM-FM. Shift registers lets me do this while only taking up a few pins on the arduino board. Instead of of 8 LEDS, each pin will be routed to a sound chip.
http://www.arduino.cc/en/Tutorial/ShiftOut
