The music causes a current to flow in wires hooked up to a squid, exciting its tissue. The video here shows an 8x microscope zoomed on the the dorsal side of the caudal fin of the Longfin Inshore Squid, which produces three colors in its process: brown, red, and yellow. The result is tough to describe--sort of like the start of a Roald Dahl painting (although he probably would've picked different tunes). Check it out below.