From the front, the ES-340 was indistinguishable from Gibson’s classic semi-hollowbody model, the ES-335, but a back view would reveal a three-piece maple neck on the 340, where the neck of the 335 was mahogany during the 340’s production run.

The real difference between the two models was in the wiring. Gibson’s traditional wiring system for two pickups was simple: separate tone and volume controls for each pickup plus a three-way switch that selected neck pickup alone, bridge pickup alone, or both pickups. That was more than enough for most players, but for those who liked a certain blend of the two pickups together, a seemingly simple adjustment in volume would cause both pickups to be changed by the exact same amount. It was difficult, if not impossible, to maintain the same pickup mix at different volumes.

Gibson solved the wiring problem by rewiring the two individual volume knobs to function as a pickup blend control and a master volume. As it turned out, there really wasn’t such a great demand for the ES-340’s system, and the model only lasted in production for five years.