A simple Processing + Arduino project modified from FrequencyEnergy to detect the beat(Kick, Snare, Hi-Hat) from the buffer and then illuminate different LEDs on your Arduino according to the beat by using the StandardFirmata to communicating Arduino and Processing. Need Arduino and Minim libraries for Processing 1.5.1. Remember to change the ledPin value and mp3 file path to your owns then make 'em glow! Details and an example here: http://www.douban.com/note/224919397/