Bah! You're all only holding part of the answer! Each one of you is
correct in part of what you say. Especially Rich. LOL
When the pickup is in humbucker mode, it will sound the same right side
up, or up side down. That's NORMAL humbucker mode. Some pickups
might be designed with two different coils for each half of the humbucker,
those are the rare exception. Also, if I'm not mistaken, the Neck pickup
is Right side up, and the bridge pickup is the one that's up side down.
As stated before, that's so when you coil tap the humbucker, the live
single coil will be the one towards the middle of the guitar.
Now, a slight change in this general rule is phasing. You can run the
phasing (which direction the electricity is pulsing through the coils)
opposite of the other pickups, but the change in tone would only be noticed
when the reverse phased pickup is used with ANOTHER pickup. Without
a second pickup activated, there is nothing for a single lonely humbucker
to be out of phase with! Often you well see single coil pickups offered
in reverse phase. This helps if you have say a strat with three pickups...
You can have the middle one out of phase for a different tone, or a
psudo humbucker when combined with the neck or bridge pickup,
depending on how it's wired (series/parellel).
Some pickups, particularly single coils have fixed (pre adjusted) pole
pieces set to a specific height. That absolutly does effect the tone of
the pickup, and flipping a pickup with fixed pole pieces will effect the tone.
Part of Jimi Hendrix's very original tone was derived from the fact that he
was using a left handed strat, right handed. Or was it the other way
around? I don't recall. But again, on a humbucker, unless you have
adjusted those pole pieces (which you can just readjust again), it will
sound the same right side up, or upside down. Again, the exception being
special design humbuckers where the two coils are different by design.
That's all I can think of right now...I'm at work so I had to type this up
at super speed so I can get back to work. I can try and clarify things
later when I get home from work. I can clear things up if you have more
I do hope this helped out some. Wiring a guitar non-standard can be a
daunting task. Not because it's hard to figure out, but because you have
so damn many options!! LOL