The following two files were used to create an Arduino-powered LED light show that synchronizes to the bass frequencies of a song. When the average volume of the audio data's low frequences passes a certain threshold, a "turn-on" signal is sent to the LED lights, giving the appearance that the lights are dancing to the song's kick drum.
The previous version only worked by specifying the location of an mp3 file, but the latest version is able to take in audio data from the computer's audio line-out, meaning that the lights are able to dance to any song you play through your computer's speakers.