Wow, check this color organ out, it almost looks like candy.
The circuit itself consists of an electret condensor microphone feeding a two stage preamplifier with a sensitivity control. The signal is then split up into three channels with individual level adjustments. Each channel has it’s own filter circuit, so that they each respond to a different range of sound frequencies, one each for treble, midrange, and bass sounds. The signal is then sent to an LED bargraph ladder circuit, with red/yellow, green/white, and blue/green leds for each channel respectively. Two LEDs were used for every one shown in the diagram, and the LED resistors were increased to 1K to extend battery life. With high output LEDs there is still lots of brightness even at lower currents, so this works well to lower current consumption. As well, there was a single purple colored UV LED included that is on whenever power is turned on.