Beaty Light Bulbs

Can anybody post a circuit diagram for a 12v low wattage car lght bulb which gets brighter and dimmer as the music increases/decreases. The reason being I have these cool sony xplod speakers in the back of my car and when I open the tailgate the interior light shines through the red translucent cone. I would like to integrate the interior bulb to a circuit so that at night the speakers light up with the beat to the music.HELP PLEASE

P.S. Can I Just wire the bulb into the speaker feed wire or will this suck too much wattage from the speaker or will it cause interference with the music?

Circuits that cause lights to pulse to music are called color organs. Do a web search for "color organ circuit" and pick one that can operate from your car's 12 volt supply. Do not attach your car's trunk light directly to your radio speaker wires.