Colour Organ

"The early history of this art was driven by an interest in color. In the eighteenth century, a Jesuit priest, Louis- Bertrand Castel, invented the first color organ. Others, including D.D. Jameson, Bainbridge Bishop, and A. Wallace Rimington, created color organs through the next century [2].
These instruments, typically controlled by playing a pianostyle keyboard, bathed a screen in everchanging colored light.... Louis Bertrand Castel - CLAVECIN OCULAIRE The French Jesuit monk Louis Bertrand Castel, the well-known mathematician and physicist, was a firm advocate of there being direct solid relationships between the seven colors and the seven units of the scale, as per Newton's Optics.
Around 1742, Castel proposed the construction of a clavecin oculaire, a light-organ, as a new musical instrument which would simultaneously produce both sound and the "correct" associated color for each note. B (dark) violet Bb agate A violet Ab crimson G red F# orange F golden yellow E yellow Eb olive green D green C# pale green C blue

A color organ splits sound into high/mid/low ranges and maps the intensity of each range to a different color on some RGB LEDs. So each sound has it's own color. In short, it makes a color light show based on your music.