am i stupid? i've never heard of this on a guitar before, someone please help
When pickups are in phase, using them together uses all the normal tone from both combined. If you get a guitar with two pickups (like a Les Paul or SG) and put the pickup selector in the middle position, you usually are hearing both pickups 'in phase' with each other. Basically think of 'in phase' meaning 'together' or 'in harmony'.

If you change pickups to be out of phase, that means one of the pickups is going 'against' the other one. If you are only using one pickup at a time, you won' hear any difference. If however you use them together when one of them is in 'reverse phase', you will get a vey different tone. When one of the pickups is in reverse phase and you have both pickups selected, the pickups aren't working together as one any more - instead, one pickup is working against the other. So you can be humbucking the humbuckers. It makes the sound quieter and clearer, usually with less mid tones, kind of like if you put a wah-wah pedal on and left it still in the middle position.

Some guitars come with the pickups wired like this stock, others have a switch to change the pickups between in phase and out of phase. Some pickups are made specifically to be out of phase (by taking the magnet out and flipping it around).

Peter Green (earlier Fleetwood Mac) and Joe Perry (Aerosmith) both famously make use of phase switching.
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Last edited by MrFlibble at Jul 7, 2009,