Fade (audio engineering)
||This article may contain original research. (May 2012)|
In audio engineering, a fade is a gradual increase or decrease in the level of an audio signal. The term can also be used for film cinematography or theatre lighting, in much the same way (see fade (filmmaking) and fade (lighting)).
A recorded song may be gradually reduced to silence at its end (fade-out), or may gradually increase from silence at the beginning (fade-in). Fading-out can serve as a recording solution for pieces of music that contain no obvious ending.
Though relatively rare, songs can fade out, then fade back in. Some examples of this are "Helter Skelter" and "Strawberry Fields Forever" by The Beatles, "Suspicious Minds" by Elvis Presley, and "Thank You" by Led Zeppelin.
The term fade is also used in multi-speaker audio systems to describe the balancing of power between front and rear channels.
Origins and early examples 
Gustav Holst's "Neptune, the mystic", part of the orchestral suite The Planets written between 1914 and 1916, is an early example of music to have a fade-out ending during performance. Holst stipulates that the women's choruses are "to be placed in an adjoining room, the door of which is to be left open until the last bar of the piece, when it is to be slowly and silently closed", and that the final bar (scored for choruses alone) is "to be repeated until the sound is lost in the distance". Although commonplace today, the effect bewitched audiences in the era before widespread recorded sound—after the initial 1918 run-through, Holst's daughter Imogen (in addition to watching the charwomen dancing in the aisles during "Jupiter") remarked that the ending was "unforgettable, with its hidden chorus of women's voices growing fainter and fainter... until the imagination knew no difference between sound and silence".
The technique of ending a spoken or musical recording by fading out the sound goes back to the earliest days of recording. In the era of mechanical (pre-electrical) recording, this could only be achieved by either moving the sound source away from the recording horn, or by gradually reducing the volume at which the performer/s were singing, playing or speaking. With the advent of electrical recording, smooth and controllable fadeout effects could be easily achieved by simply reducing the input volume from the microphones using the fader on the mixing desk.
No single recording can be reliably identified as "the first" to use the technique. In 2003, on the (now-defunct) website Stupid Question, John Ruch listed the following recordings as possible contenders:
Bill Haley’s cover version of "Rocket 88" (1951) fades out to indicate the titular car driving away. There are claims that The Beatles’ "Eight Days a Week" (recorded 1964) was the first song to use the reverse effect—a fade-in.
However an even earlier example that uses this effect is an 1894 78 rpm record called "The Spirit of ’76", a narrated musical vignette with martial fife-and-drum that gets louder as it 'nears' the listener and quieter as it 'moves away'.
The fade-out as a simulation of a moving sound source seems to continue right up to "Rocket 88". Other examples aren’t so obvious (though fade-out may always imply that the song continues forever and we’re only passing by it for a few minutes).
There are early examples that appear to bear no obvious relationship to movement. One is "Barkin’ Dog" (1919) by the Ted Lewis Jazz Band. Another contender is "America" (1918), a patriotic piece by the chorus of evangelist Billy Sunday.
By the early 1930s longer songs were being put on both sides of records, with the piece fading out at the end of Side One and fading back in at the beginning of Side Two. Records at the time held only about two to five minutes of music per side. The segue allowed for longer songs (such as Count Basie’s "Miss Thing"), symphonies and live concert recordings.
However, shorter songs continued to use the fade-out for unclear reasons—for example, Fred Astaire’s movie theme "Flying Down to Rio" (1933). Even using fade-out as a segue device doesn’t seem obvious, though we certainly take it for granted today.It is possible that movies were an influence here. Fade-ins and fade-outs are often used as cinematic devices that begin and end scenes; film language that developed at the same time as these early recordings. The term 'fade-out' itself is of cinematic origin, appearing in print around 1918. And jazz, a favorite of early records, was a popular subject of early movies too.
More recently: "For Henri Lefebvre (1971a:19), 'everyday life in the modern world' is a privileged site for the crucial fact of recurrence. The question of how to end a song now becomes pressing. The answer, often, is not to end: the harmonically inconclusive or artificially abrupt finish, or - quintessentially - the fade. As Sean Cubitt points out (1984: 210), this refers us"
to the activity of the auditor, with whom lies the only available fulfillment...[It] pledges that the performer...has an existence beyond the recording...This refusal of completion refers us, not back into the song, as is the case with the classic aesthetic object but outwards to the ways in which the song is heard.
"At the meta-song level, the prevalence of pre-taped sequences (for shops, pubs, parties, concert intervals, aircraft headsets) emphasizes the importance of flow. The effect on radio pop programme form [are] a stress on continuity achieved through the use of fades, voice-over links, twin-turntable mixing and connecting jingles."
A fader is any device used for fading, especially when it is a knob or button that slides along a track or slot. A knob which rotates is usually not considered a fader, although it is electrically and functionally equivalent. A fader can be either analogue, directly controlling the resistance or impedance to the source (e.g. a Potentiometer); or digital, numerically controlling a digital signal processor (DSP). A fader can also be used as a control for a voltage controlled amplifier, which has the same effect on the sound as any other fader, but the audio signal does not pass through the fader itself. Digital faders are also referred to as virtual faders, since they can be viewed on the screen of a digital audio workstation. Modern high end digital mixers often feature "flying faders", faders with piezo-electric actuators attached; such faders can be multi-use and will jump to the correct position for a selected function or saved setting. Flying faders can be automated, so that when a timecode is presented to the equipment, the fader will move according to a previously performed path.
A crossfader on a DJ mixer essentially functions like two faders connected side-by-side, but in opposite directions. It allows a DJ to fade one source out while fading another source in at the same time. This is extremely useful when beatmatching two sources of audio (or more, where channels can be mapped to one of the two sides of the crossfader individually) such as phonograph records, compact discs or digital sources.
The technique of crossfading is also used in audio engineering as a mixing technique, particularly with instrumental solos. A mix engineer will often record two or more takes of a vocal or instrumental part and create a final version which is a composite of the best passages of these takes by crossfading between each track.
In the perfect case, the crossfader would keep constant output level. However, there's no standard on how this should be achieved. Many DJ equipment manufacturers offer different mixers for different purposes (e.g. scratching, beatmixing, cut mixing, etc.). High-end mixers often have crossfade curve switches allowing the DJ to select the type of crossfade necessary. Experienced DJs are also able to crossfade between tracks using the channel faders.
Pre-fader, post-fader 
On a mixer with auxiliary send mixes, the send mixes are configured pre-fader or post-fader.
If a send mix is configured pre-fader, then changes to the main channel strip fader does not affect the send mix. In live sound reinforcement, this is useful for stage monitor mixes where changes in the Front of House channel levels would distract the musicians. In recording and post production, configuring a send to be pre-fader allows the amount of audio sent to the aux bus to remain unaffected by the individual track fader.
See also 
- Nisbett, Alec (1966). The Technique of the sound studio. Focal Press.
- Everett, Walter (2008). The Foundations of Rock: From "Blue Suede Shoes" to "Suite: Judy Blue Eyes". Oxford University Press. p. 171. ISBN 0195310233.
- Patterson, Nigel; Piers Beagley. "'Suspicious Minds': Elvis' Greatest Single?". Elvis Information Network. Retrieved September 2, 2010.
- Huron, David (2006). Sweet Anticipation: Music and the Psychology of Expectation. MIT Press. p. 318. ISBN 0262083450.
- "The Planets" (full orchestral score): Goodwin & Tabb, Ltd., London, 1921
- "The Great Composers and Their Music", Vol. 50, Marshall Cavendish Ltd., London, 1985. I.H. as quoted on p1218
- Stupid Question Archive
- Middleton, Richard (1990/2002). Studying Popular Music, p. 95-6. Philadelphia: Open University Press. ISBN 0-335-15275-9.
- Evolution of the DJ crossfader Retrieved 13-06-2008