This is part of some investigation I've been doing into how the positioning of a pickup affects tone. Discussions about what lies behind the distinctive tones of classic guitars too often concentrate on things like the electronic charateristics of the pickups or the woods used for necks and bodies. While those factors certainly contribute they are by no means the "be all and end all". They do not, for example, explain the changes in tone when different pickups are selected on multi-pickup guitars. To understand guitar sounds you need to understand the significance of pickup placement.

This diagram gives a very simplified picture. For a start, the levels of the different harmonics will vary and they are unlikely to all be equal in magnitude as in the diagram. Also, the diagram deals only with open strings. If you fret a string then you change it's effective length and the positions of the harmonic nodes will shift relative to the positions of the pickups. Nevertheless I think I have made a start towards understanding what really causes the differing tonal characteristics of electric guitars.

Note, for example, how the neck pickups of strats and telecasters sit over nodes for the 3rd and 7th harmonics, which presumably means these are mostly absent from the tone of the guitar's open strings when only the neck pickup is selected. Contrast with the neck pickups for Gibson Les Pauls.

(NB: The magnitude of vibration is greatly exaggerated in the diagram to better illustrate the positions of nodes and anti-nodes.)