Editing Effects unit (section)

===Feedback/sustain===

''[[Audio feedback]]'': Audio feedback is an effect produced when amplified sound is picked up by a microphone or guitar pickup and played back through a [[guitar amplifier]], initiating a "feedback loop", which usually consists of high-pitched sound. Feedback that occurs from a vocal mic into a [[PA system]] is almost always avoided. However, in some styles of rock music, electric guitar players intentionally create feedback by playing their instrument directly in front of a heavily amplified, [[distortion (music)|distorted]] [[guitar amplifier]]'s [[speaker enclosure]]. The creative use of feedback effects was pioneered by guitarists such as [[Jimi Hendrix]] in the 1960s. This technique creates sustained, high-pitched [[overtone]]s and unusual sounds not possible through regular playing techniques. Guitar feedback effects can be difficult to perform, because it is difficult to determine the sound volume and guitar position relative to a guitar amp's loudspeaker necessary for achieving the desired feedback sound.<ref>Wright, Ed (2007). [https://books.google.com/books?id=ysmj8vITtzcC ''Left-Handed History of the World''], Murdoch Books. p. 209.</ref><ref>Amelar, Chris (1997). [https://books.google.com/books?id=KsV_l0FeKlwC ''The Guitar F/X Cookbook''], Hal Leonard. p. 41.</ref> Guitar feedback effects are used in a number of rock genres, including [[psychedelic rock]], [[heavy metal music]] and [[punk rock]].
[[File:EBow.jpg|thumb|left|upright|An [[EBow]] guitar string resonator]]

[[EBow]] is a [[brand name]] of Heet Sound Products, of Los Angeles, California, for a small, handheld, battery-powered resonator. The Ebow was invented by Greg Heet, as a way to make a note on an electric guitar string resonate continuously, creating an effect that sounds similar to a bowed violin note or a sustained [[pipe organ]] note. The resonator uses a [[Pickup (music technology)|pickup]] – inductive string driver – feedback circuit, including a sensor coil, driver coil, and amplifier, to induce forced string resonance. The Ebow brand resonator is monophonic, and drives only one string at a time.

Other handheld and mounted guitar and bass resonators have been on the market since the early 1990s, produced in Germany under the SRG brand, which ceased production in 2016, and were available in both monophonic (one string at a time) and polyphonic (multiple strings at a time) models, which included multiple onboard trigger switch effects, such as HPF (high pass filter) for enhancing harmonics and producing feedback effects, and LPF (low pass filter), producing a bass boost with a cello sound on heavy gauge strings.<ref>{{Cite web |url=http://www.effectsdatabase.com/model/srg/d1 |title=Archived copy |access-date=4 May 2020 |archive-date=20 January 2022 |archive-url=https://web.archive.org/web/20220120202528/https://www.effectsdatabase.com/model/srg/d1 |url-status=dead }}</ref> Later EBow models, such as the plus Ebow, contain a mode slide switch on the back, which allows the player to either produce just sustain or [[overtone]] feedback in addition to sustain.<ref name="The Contemporary Guitar"/> Pedals such as the Boss DF-2 and FB-2 use an internally generated signal matched to the pitch of the guitar that can be sustained indefinitely by depressing the pedal. Many [[#Dynamics|compressor pedals]] are often also marketed as "sustainer pedals". As a note is sustained, it loses energy and volume due to diminishing vibration in the string. The compressor pedal boosts its electrical signal to the specified [[dynamic range]], slightly prolonging the duration of the note.<ref>Hunter, Dave (2004). [https://books.google.com/books?id=7DjYrk7Vap4C ''Guitar Effects Pedals: The Practical Handbook'']. Hal Leonard. p. 25.</ref> This, combined with heavy distortion and the close proximity of the guitar and the speaker cabinet, can lead to infinite sustain at higher volumes.