Sound and effects

Flanging, compression/sustain, overdrive, delay, reverb, digital and software effects ...
Sound and effects While an acoustic guitar's sound is largely dependent on the vibration of the guitar's body and the air within it, the sound of an electric guitar is largely dependent on a magnetically induced electrical signal, generated by the vibration of metal strings near sensitive pickups. The signal is then "shaped" on its path to the amplifier by using a range of effect devices or circuits that modify the tone and characteristics of the signal. The most basic sound-shaping circuitry are the volume control (potentiometer), tone control (which "rolls off" the treble frequencies), and the pick-up selectors which are found on most electric guitars, and the gain and tone (usually consisting of at least bass and treble) controls on the guitar amplifier.

In the 1960s, some guitarists began exploring a wider range of tonal effects by distorting the sound of the instrument. To do this, they increased the gain, or volume, of the preamplifier, which produced a "fuzzy" sound. This effect is called "clipping" by sound engineers, because when viewed with an oscilloscope, the wave forms of a distorted signal appear to have had their peaks "clipped" off. This was not actually a new development in the instrument, but rather a shift of aesthetics. This sound was not generally recognized previously as desirable. In the 1960s, the tonal palette of the electric guitar was further modified by introducing an effects box in its signal path. Traditionally built in a small metal chassis with an on/off foot switch, such "stomp boxes" have become an important part of the electric guitar tone in many genres. Typical effects include stereo chorus, fuzz, wah-wah and flanging, compression/sustain, delay, reverb, and phase shift. Not all special effects are electronic; in 1967, guitarist Jimmy Page of The Yardbirds and Led Zeppelin created unusual, psychedelic sound effects by playing the electric guitar using a violin bow with a delay pedal and wah pedal.
In the 1970s, as effects pedals proliferated, their sounds were combined with tube distortion at lower, more controlled volumes by using power attenuators such as Tom Scholz' Power Soak as well as re-amplified dummy loads such as Eddie Van Halen's use of a variac, power resistor, post-power-tube effects, and a final solid-state amp driving the guitar speakers. A variac is one approach to power-supply based power attenuation, to make the sound of power-tube distortion more practically available.

By the 1980s and 1990s, digital and software effects became capable of replicating the analog effects used in the past. These new digital effects attempted to model the sound produced by analog effects and tube amps, to varying degrees of quality. There are many free guitar effects computer programs for computers that can be downloaded via the Internet. Now, computers with sound cards can be used as digital guitar effects processors. Although digital and software effects offer many advantages, many guitarists still use analog effects.

In 2002, Gibson announced the first digital guitar, which performs analog-to-digital conversion internally. The resulting digital signal is delivered over a standard Ethernet cable, eliminating cable-induced line noise. The guitar also provides independent signal processing for each individual string. Also, in 2003 amp maker Line 6 released the Variax guitar. It differs in some fundamental ways from conventional solid-body electrics. For example it uses piezoelectric pickups instead of the conventional electromagnetic ones, and has an on-board computer capable of modifying the sound of the guitar to model the sound of many instruments.

Extended playing techniques
The sound of a guitar is not only adapted by electronic sound effects, but also heavily by all kinds of new techniques developed or becoming possible in combination with the electric amplification. This is called extended technique. Famous extended techniques are the use of the tremolo, as mentioned above, playing harmonics, palm muting, shred guitar, tapping, pinch harmonic, dive bomb. These are all common techniques mainly used in hard rock and heavy metal. Also other techniques exist, such as playing with audio feedback and alternate tunings. Sometimes guitars are even adapted with extra modifications to alter the sound, examples: usage of the slide, prepared guitar and 3rd bridge.