Source: http://www.theatlantic.com/technology/ar...

The history of guitar-signal modification is one of happy accidents. Any “unmistakable” guitar sound isn’t just the product of a gifted musician, nor is it just the result of cultural context; it’s contingent on the combined work of transistors, speakers, magnets, signals, wires, and diodes.

Consider how many transformations take place during the production of sound from an electric guitar. The guitarist picks a string with a plastic plectrum, which produces vibrations that are picked up by coiled magnets directly positioned behind the strings, inducing an alternating current (hence the name “pick-ups”). The current’s signal is then transmitted through a wire lead, after which it’s amplified by either a vacuum tube or solid-state amplifier, and then reshaped into audible sound by a loudspeaker. Depending on the sound that a guitarist is seeking, he or she may place guitar effect pedals, or stompboxes, in between the pick-ups and the amplifiers. These small, intermediary devices further manipulate the guitar signal to produce a multitude of effects.