Step 1: Gather Materials
1x sound triggered car effects light with adjustment dial
1x shallow "new work" wall gang box
1x three prong wall outlet
1x wall outlet cover plate
1x 12v relay (the higher the amperage it can handle the better off you'll be)
1x project box (to hold control circuit)
1x computer power cord (the thicker its wire the better)
1x 12v AC adapter
knife/ dremel (to work cases and open the light)
Step 2: Deciphering the Light Controller
That being said, hook the light's power wires to the lines coming from the 12v AC adapter, making sure you can make the light function as it's meant to, usually with a normally on, and variable sensetivity audio triggered mode.
Now get your multimeter, set the light to a sensetivity that you can trigger it with your voice, and probe for a spot on the board (probably somewhere near the middle) that is at 12v when the light is on, and 0v when the light's off. these two points are what you will attach the coil of the relay to later on. You may want to mark them for later reference. Different brands of lights will likely have different boards, but the concept of how they work should be similar enough for our purposes.
Step 3: Much Bashing and Breaking
Alternatively, you could also just add a barrel plug to your project box and use the adapter as is, but it's not as slick if you have to use two outlets to power this box now is it?
Now that you have the power source for your light's board laid bare, you'll want to do the same for the control board in your light as well. pull the board out of it's case, keeping about 6" of the the 12v power cord on, but cutting or desoldering the lines that feed the tube of the light itself. these are those high voltage ones we talked about earlier, and you want to make those as small a target for finger touching as possible.
Step 4: Connect the Bits and Bobs
Step 5: Testing and Assembly
Once you're happy with how it works, you can start putting it in the casing. For mine, I melted a hole in the case for the adjustment dial to stick out of, made a hole for the power cable to sit in (knot the power cable so it won't come out), and made a notch for the wires feeding the outlet to exit the project box from. I then mounted the outlet in the gang box, added it's cover plate, and super glued the gang box to the project box so that if I need to I can take the screws of the box off and get to the insides again. I also glued the boards and relays into the project box so they don't go anywhere.
Step 6: Completion and Usage
Other than that, You just need to hook the BandBlinker up to your BandBlinder or even a desk lamp or other light and rock away. Hope you found this instructable helpful.