This is old-school, but I don't want to re-invent the wheel here. I'm sure there is a schematic somewhere for a circuit that does this. It is very similar to a color organ that was popular in the '70s, but in this case, it is one channel and we don't care about filtering frequencies. The only thing I want is for a light bulb (Not an LED) to grow brighter and dimmer in sync with the amplitude of an audio signal. No audio, no light. Full volume audio, Light at full brightness, and everything inbetween, with the light reacting as the audio plays. I don't want to use a mic pickup for this. I would prefer a line level audio input, but most of these seemed to use a fully amplified signal to drive it. That's OK, just not my first choice. I found this long discontinued kit still listed on a website: http://www.omnitronelectronics.net/phpstore/html/K4738-120VAC-Single-Channel-Color-Organ-Kit-solder-kit-723.html. Somewhere I found a video of this working, and the effect is exactly what I'm looking for. The owner of the website says it's discontinued, so if you go there and it's not showing up, he may have taken it down after being alerted to it. I want the incandescent bulb because of it's natural tendency to smooth out the variations in brightness due to its relatively long fading due to the filament. Something that would take a much more complicated circuit to reproduce with LEDs. Can anyone guide me in the right direction?