Effect : Chorus, Vibrato, Harmonic Exciter, Sustainer
Frequency effect : Chorus, Vibrato, Harmonic Exciter, Feedbacker/sustainer
Chorus effect
To produce the effect, individual sounds with roughly the same timbre and nearly (but never exactly) the same pitch converge and are perceived as one, an effect which is created naturally in a choir of singers or a string orchestra. The effect creates this sound by splitting the signal into a vibrato effect and a clean path, so that the output is the sum of these inputs. A good quality chorus effect creates a rich, shimmering quality or a double-tracking effect when it is used subtly. It creates a "spacey" sound if it is used in a more pronounced fashion. Better-quality stompbox chorus pedals and almost all rackmount chorus units have stereo outputs, because the chorus effect is more effective when it is heard in stereo.
Pitch shifter effect
An effect which enables a user to transpose the pitch of the input signal. The simplest pitch shift effects can add octaves above or below the input pitch. More sophisticated pitch shifters can add fourths or fifths. Some 2000s-era pitch shifters can harmonize an input pitch in thirds or sixths, based on the key that is set by the user. This allows a performer to play a melody and have it harmonized like a duo. Pitch shift devices often allow the user to mix the input signal with the effected signal, thus creating a thicker, richer sound (e.g., parallel octaves or fifths). Some pitch shifters can also add very tiny shifts in pitch, thus creating a chorus-like effect. The Harmonizer brand pedal can change the input pitch up or down any interval. Some pitch shifters, such as the Digitech Whammy have a treadle-style footpedal which allows users to create "whammy bar" note-bending effects. The Electro-Harmonix Polyphonic Octave Generator can produce pitches an octave below the note being played, or one or two octaves above the note being played.
Vibrato effect
Vibrato refers to a variation in frequency of a note. This is done naturally when an opera singer or violin player holding one note for a long time varies the frequency up and down using a fraction of a semitone. Most vibrato effects have a "rate" knob which allows the performer to set how fast the variation will occur. Some vibrato effects also have a "depth" knob that controls the pitch difference in the variation. A vibrato with a very shallow depth (e.g., a fraction of a semitone) can be a subtle effect. A vibrato with an exaggerated "depth" setting (e.g., half of a semitone or more) will produce a more dramatic, ululating sound. Electronically, the vibrato effect is created by taking a sine wave applied as input to a voltage-controlled oscillator.
Guitarists often use the terms "vibrato" and "tremolo" inconsistently. A so-called vibrato unit in a guitar amplifier actually produces tremolo, while a tremolo arm on a guitar produces vibrato. However, finger vibrato is genuine vibrato.
Harmonic Exciter/ psychoacoustic exciter
This effect, which is also known as a "psychoacoustic exciter", adds upper harmonic content and a subtle amount of controlled harmonic distortion to a sound source, which creates a richer tone colour in the upper mid and treble part of the spectrum. Unlike many effects, the Aural Exciter is not usually used in "real time" during the recording. It is usually added to the vocals or the entire track in the post-production stage. The effect was developed in the mid-1970s to add "brightness" to reel-to-reel tape mixes that had lost clarity due to repeated overdubs. Aphex, the company that invented the first "Aural Exciter" effect, claims that the effect provides increased presence and clarity, restored natural brightness, greater perceived loudness, and improved detail and intelligibility.
Feedbacker/sustainer
While audio feedback in general is undesirable due to the high frequency overtone, when controlled properly, it can provide true sustain of the sound (instead of using a distortion/compressor to make quiet notes louder, or a feedback of a signal in a circuit as in a delay unit). Several approaches have been used to produce guitar feedback effects, which sustain the sound from the guitar. The most primitive form, as used by for example Jimi Hendrix, is to use the feedback created when the guitar is played in front of an instrument amplifier's loudspeaker when it is set to a high volume.
The neck pickup can be replaced by a magnetic string driver to push the strings based on the bridge pickup, such as the Sustainiac Sustainer and Fernandes Sustainer. A string driver can be mounted on a stand as in the Guitar Resonator. Feedback start, stop and harmonics can be controlled here by positioning the drivers distance to the strings and the position along the guitar neck while playing. A signal amplifier can be used to power the headstock transducer, which in turn sends feedback vibration down the string, as in Sustainiac's Model C. A handheld string driver can contain a pickup and driver, as in the EBow, which uses a small inductor coil to vibrate the string, creating a bow-like sustained sound. A dedicated high-gain guitar amplifier can be used in the control room, without a microphone, as a footswitch-controlled string feedback driver. The microphone is placed on the speaker cabinet of the main guitar amp in the isolation booth or live room.
Chorus effect
To produce the effect, individual sounds with roughly the same timbre and nearly (but never exactly) the same pitch converge and are perceived as one, an effect which is created naturally in a choir of singers or a string orchestra. The effect creates this sound by splitting the signal into a vibrato effect and a clean path, so that the output is the sum of these inputs. A good quality chorus effect creates a rich, shimmering quality or a double-tracking effect when it is used subtly. It creates a "spacey" sound if it is used in a more pronounced fashion. Better-quality stompbox chorus pedals and almost all rackmount chorus units have stereo outputs, because the chorus effect is more effective when it is heard in stereo.Pitch shifter effect
An effect which enables a user to transpose the pitch of the input signal. The simplest pitch shift effects can add octaves above or below the input pitch. More sophisticated pitch shifters can add fourths or fifths. Some 2000s-era pitch shifters can harmonize an input pitch in thirds or sixths, based on the key that is set by the user. This allows a performer to play a melody and have it harmonized like a duo. Pitch shift devices often allow the user to mix the input signal with the effected signal, thus creating a thicker, richer sound (e.g., parallel octaves or fifths). Some pitch shifters can also add very tiny shifts in pitch, thus creating a chorus-like effect. The Harmonizer brand pedal can change the input pitch up or down any interval. Some pitch shifters, such as the Digitech Whammy have a treadle-style footpedal which allows users to create "whammy bar" note-bending effects. The Electro-Harmonix Polyphonic Octave Generator can produce pitches an octave below the note being played, or one or two octaves above the note being played.
Vibrato effect
Vibrato refers to a variation in frequency of a note. This is done naturally when an opera singer or violin player holding one note for a long time varies the frequency up and down using a fraction of a semitone. Most vibrato effects have a "rate" knob which allows the performer to set how fast the variation will occur. Some vibrato effects also have a "depth" knob that controls the pitch difference in the variation. A vibrato with a very shallow depth (e.g., a fraction of a semitone) can be a subtle effect. A vibrato with an exaggerated "depth" setting (e.g., half of a semitone or more) will produce a more dramatic, ululating sound. Electronically, the vibrato effect is created by taking a sine wave applied as input to a voltage-controlled oscillator.
Guitarists often use the terms "vibrato" and "tremolo" inconsistently. A so-called vibrato unit in a guitar amplifier actually produces tremolo, while a tremolo arm on a guitar produces vibrato. However, finger vibrato is genuine vibrato.
Harmonic Exciter/ psychoacoustic exciter
This effect, which is also known as a "psychoacoustic exciter", adds upper harmonic content and a subtle amount of controlled harmonic distortion to a sound source, which creates a richer tone colour in the upper mid and treble part of the spectrum. Unlike many effects, the Aural Exciter is not usually used in "real time" during the recording. It is usually added to the vocals or the entire track in the post-production stage. The effect was developed in the mid-1970s to add "brightness" to reel-to-reel tape mixes that had lost clarity due to repeated overdubs. Aphex, the company that invented the first "Aural Exciter" effect, claims that the effect provides increased presence and clarity, restored natural brightness, greater perceived loudness, and improved detail and intelligibility.
Feedbacker/sustainer
While audio feedback in general is undesirable due to the high frequency overtone, when controlled properly, it can provide true sustain of the sound (instead of using a distortion/compressor to make quiet notes louder, or a feedback of a signal in a circuit as in a delay unit). Several approaches have been used to produce guitar feedback effects, which sustain the sound from the guitar. The most primitive form, as used by for example Jimi Hendrix, is to use the feedback created when the guitar is played in front of an instrument amplifier's loudspeaker when it is set to a high volume.
The neck pickup can be replaced by a magnetic string driver to push the strings based on the bridge pickup, such as the Sustainiac Sustainer and Fernandes Sustainer. A string driver can be mounted on a stand as in the Guitar Resonator. Feedback start, stop and harmonics can be controlled here by positioning the drivers distance to the strings and the position along the guitar neck while playing. A signal amplifier can be used to power the headstock transducer, which in turn sends feedback vibration down the string, as in Sustainiac's Model C. A handheld string driver can contain a pickup and driver, as in the EBow, which uses a small inductor coil to vibrate the string, creating a bow-like sustained sound. A dedicated high-gain guitar amplifier can be used in the control room, without a microphone, as a footswitch-controlled string feedback driver. The microphone is placed on the speaker cabinet of the main guitar amp in the isolation booth or live room.