Series-Parallel switch, more power from 2 single coils! (or less power from a humbucker).
This is an easy modification!
You can add power to a 2-single coil bass and get a meaty sound! I did it to my washburn bass (and to 3-4 friends' basses), the sound now is louder and fuller.
I also did this to a lot of friends' Strats, so the result is that you have your normal guitar (or bass), along with an extra sound, more powerful and hum-cancelling.
I do the opposite thing to humbuckers. Meaning that when you have a humbucker, you can wire it in series (usual fat sound) or parallel (still humbucking but with more treble,less bass and a little less volume).
