help with possible lighting mod

[YonjaminYodle]

I have another idea I'd like to implement in my 5150 before I go on the road (see previous post)....
I'd like to put a light (either flourescent or otherwise) in the head unit and have it turn on or off based on sound coming through the cabs. As in, off when Im not playing, on when I am...and possibly a dimmer somehow.

Now, firstly would it generate EMI enough to make a hum?

My first idea would be that this could be achieved by tapping into the "output jack" and running it through a circuit with some sort of resistor setup first to power the light. Would this diminish the sound comign through it?

Any ideas will be entertained, thanks in advance.

[EC8010]

I've moved this thread to this forum as it is more likely to generate a response.