At ladyada’s tea party, user mtbf0 has posted details of his RGB brain machine powered by a Boarduino.

…it generates a base frequency at 200Hz. Offset frequencies of 201Hz-217Hz in 1Hz increments can be selected giving binaural beats in the range of 1Hz-17Hz. The LEDs are controlled by comparing the phases of the base and offset waveforms, so although the code’s a little hairier than Mitch’s, adding new frequencies is easy.

Trippy RGB brain machinuino