Right, this has nothing to do with Peter Green. I have a P-90 equipped Les Paul with the pups out of phase in the middle position for hum cancelling.

I never used the tone knobs so I decided to put them to use as high-pass instead of low pass filters

I wired the "hot" from each pickup to the centre lug of the tone pot and then wired a .0047uf cap to the two outer lugs, and then jumped a lead to the volume pot centre lug and moved the cable running to the 3-way selector to one of the outer lugs. On zero on the tone knob there is no change to the sound, and on ten there is a attenuation of the bass (This cap was used for this on the bridge pickup in vintage Rickenbackers).

First up, the big difference was probably down to the fact that there was no more tone cap as such in the circuit, which to my ears really opened up the sound of the guitar. With the tone on zero the pickups sound really natural and "breathe" more than before. The bass attenuation is slight but nonetheless perceptible with the tone on ten. It really works to improve note definition when playing arpeggios with distortion, or just to take away some of the muddiness, or indeed as Rickenbacker intended, to give just a tad more jangle.

The .0047uf cap also causes a phase shift of 90 degrees, which means that in the centre position the pickups no longer have to be 180 degrees out of phase. With the tone of one pickup on 0 and the other on 10 they are 90 degrees out of phase. What is really cool, though, is balancing the tone controls to get out of phase settings that are somewhere in between 90 and 180. It also means that the starting phasal position of the individual pickups can be moved i.e. with both tone controls on 5 the pickups are in phase but the phase has been moved 45 degrees from where it actually should be (more or less, presuming that the taper of the pots is completely linear, which it probably isn't)

Obviously, the positions of the tone knobs are relevant to one another when both pickups are selected. You have to fiddle around with it but you can get some seriously cool sounds, some that sound good both distorted and clean and some that sound good with one or the other. Balancing the volume of each pickup also reaps rewards. Some settings give a really cool Mick Ronson "c.o.c.k.ed wah" (for some reason the forum won't let me write ****) sound. A 90 degree (0 on the bridge and 10 on the neck tone) setting gives a cool boxy lead sound with great definition.

I think it has made the the guitar more flexible. Have you even been in a situation where you felt the bridge was just a tad too bright but that the mid position was just a tad too muddy. This allows you to strike a happier balance. I would also imaging that you could tailor the response of the guitar to suit the tonality of whatever amp/effect you are using. I know I have some favourite effects that don't necessarily play well with every guitar because of certain frequencies that dominate.

I also intend to install at least one push/pull pot to allow me to take the volume and tone pots completely out of the circuit, to get even more juice from the pups.

Anyways, I thought I would share it with all of you. I'm sure there are some of you out there who rarely if ever move the volume and tone controls down from ten. This has certainly gotten me using them more than I have in the past.

I am also quite sure that depending on your needs certain higher cap values might produce better results. I would also say that the type of cap could potentially make more of a difference here than it would with a regular tone control as it is directly in the circuit. I used a couple of black beauties I had lying around.

Any sound bites? Sounds kinda cool!

I did this with a Telecaster and I could cop a Stratocaster #2 position all day in that position. I used a .005 cap. It was not adjustable though. Only 90 degrees shift. I found this information digging in the forum for Bill Lawrence pickups. I had the cap switched in, in series with the neck pickup. Using a 5 position switch with the Tele I could get:
1 - Neck
2 - Neck/Bridge [Strat like phase shift] 90 degrees
3 - Parallel
4 - Series
5 - Bridge

This is a VERY cool and useful alteration.

Sorry, no sound bites (not yet anyway). I only did it this morning.

When you think about it more often than not the problem with a pickup is not that it is too bright but that it is too muddy. So a tone control that takes out bass is in many ways more useful.

I also think that with a guitar like a Les Paul, which is inclined to be quite bassy and heavy sounding a little extra air sometimes doesn't go astray.

It is quite a subtle thing, but we have all been in situation where there is just a little something about our sound which we would like to tweak. I suppose it is a sort of phasal eq, but compared to an actual eq it is completely natural sounding. I think this could work well for folks who use a parametric eq to take out/add in tiny dips and peaks in their sound.