Hey guys , i've heard several people inquiring as to how they could make leds blink or flash in time to their playing , its as simple as some leds, a transistor and a 3way switch, Some basic knowledge on circuits such as parallel and series would help you greatly - I found this on a website that gives a simple circuit :-
http://www.makezine.com/blog/archive/2006/...ve_blinkin.html
To use this circuit it needs to be modified , i've written how and drawn a diagram.
Where the p2 connector is you merely connect to the 2 wires going to your jack and where it says 12vdc you can use any power you like such as 9v as long as you remember to change the leds you have connected where it says - The 3 way switch means you can choose between on, off or blinking.
Here is a simplified version drawn by myself - I in no way claim to have designed this circuit.
I accept no liability for you building this circuit and damaging stuffs, this is a freely available document I found on the internet and merely provided some info on how you could change it slightly to meet your needs, In theory I believe this should work but I suggest you try it yourself using temporary joins etc before installing into a guitar. ( I HAVE NOT DONE THIS MYSELF, AND CANNOT CONFIRM IT WILL WORK)
P.S- Make sure you have those leds wired up right, you may fry one if not - or they may not light if you do not know how to wire your leds correctly, remember if you plan on using leds that require less voltage/current than your power is providing then use a resistor( It's advisable to use a current limiting resistor anyway )