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Audio mi xing (recorded music)

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Digital Mi xing Console Sony DMX R-100 used in project studios

Insound recording and reproduction,audio mi xingis the process of optimizing and combiningmultitrack recordingsinto a finalmono,stereoorsurround soundproduct. In the process of combining the separate tracks, their relative levels are adjusted and balanced and various processes such asequalizationandcompressionare commonly applied to individual tracks, groups of tracks, and the overall mix. In stereo and surround sound mi xing, the placement of the tracks within the stereo (or surround) field are adjusted and balanced.[1]: 11, 325, 468 Audio mi xing techniques and approaches vary widely and have a significant influence on the final product.[2]

Audio mi xing techniques largely depend onmusic genresand the quality of sound recordings involved.[3]The process is generally carried out by ami xing engineer,though sometimes therecord producerorrecording artistmay assist. After mi xing, amastering engineerprepares the final product for production.

Audio mi xing may be performed on ami xing consoleor in adigital audio workstation.

History[edit]

In the late 19th century,Thomas EdisonandEmile Berlinerdeveloped the first recording machines. The recording and reproduction process itself was completely mechanical with little or no electrical parts. Edison'sphonograph cylindersystem utilized a small horn terminated in a stretched, flexible diaphragm attached to a stylus which cut a groove of varying depth into the malleable tin foil of the cylinder. Emile Berliner's gramophone system recorded music by inscribing spiraling lateral cuts onto a vinyl disc.[4]

Electronic recording became more widely used during the 1920s. It was based on the principles of electromagnetictransduction.The possibility for a microphone to be connected remotely to a recording machine meant that microphones could be positioned in more suitable places. The process was improved when outputs of the microphones could be mixed before being fed to the disc cutter, allowing greater flexibility in the balance.[5]

Before the introduction ofmultitrack recording,all sounds and effects that were to be part of a recording were mixed simultaneously during a live performance. If the recorded mix was not satisfactory, or if one musician made a mistake, the selection had to be performed over until the desired balance and performance was obtained. The introduction of multi-track recording changed the recording process into one that generally involves three stages:recording,overdubbing,and mi xing.[6]

Modern mi xing emerged with the introduction of commercial multi-track tape machines, most notably when8-track recorderswere introduced during the 1960s. The ability to record sounds into separate channels made it possible for recording studios to combine and treat these sounds not only during recording, but afterward during a separate mi xing process.[7]

The introduction of thecassette-basedPortastudioin 1979 offered multi-track recording and mi xing technology that did not require the specialized equipment and expense of commercial recording studios.Bruce Springsteenrecorded his 1982 albumNebraskawith one, and theEurythmicstopped the charts in 1983 with the song "Sweet Dreams (Are Made of This)",recorded by band memberDave Stewarton a makeshift 8-track recorder.[8]In the mid-to-late 1990s, computers replaced tape-based recording for most home studios, with thePower Macintoshproving popular.[9]In the mid-1980s, many professional recording studios began to usedigital audio workstations(DAWs) to accomplish recording and mi xing previously done with multitrack tape recorders, mi xing consoles, and outboard gear.

Equipment[edit]

Mi xing consoles[edit]

A simple mi xing console
Main article:Mi xing console

A mixer (mi xing console,mi xing desk, mi xing board, or software mixer) is the operational heart of the mi xing process.[10]Mixers offer a multitude of inputs, each fed by a track from a multitrack recorder. Mixers typically have 2 main outputs (in the case of two-channel stereo mi xing ) or 8 (in the case of surround).

Mixers offer three main functionalities.[10][11]

  1. Summing signals together, which is normally done by a dedicated summing amplifier or, in the case of a digital mixer, by a simple algorithm.
  2. Routing of source signals to internal buses or external processing units and effects.
  3. On-board processors with equalizers and compressors.

Mi xing consoles can be large and intimidating due to the exceptional number of controls. However, because many of these controls are duplicated (e.g. per input channel), much of the console can be learned by studying one small part of it. The controls on a mi xing console will typically fall into one of two categories: processing and configuration. Processing controls are used to manipulate the sound. These can vary in complexity, from simple level controls, to sophisticated outboard reverberation units. Configuration controls deal with the signal routing from the input to the output of the console through the various processes.[12]

Digital audio workstations(DAW) can perform many mi xing features in addition to other processing. Anaudio control surfacegives a DAW the same user interface as a mi xing console.[12]

Outboard and plugin-based processing[edit]

Outboard audio processing units (analog) and software-basedaudio plug-ins(digital) are used for each track or group to perform variousprocessingtechniques. These processes, such as equalization, compression, sidechaining, stereo imaging, and saturation are used to make each element as audible and sonically appealing as possible. The mix engineer also will use such techniques to balance thespaceof the final audio wave; removing unnecessary frequencies and volume spikes to minimize the interference orclashingbetween each element.

Processes that affect signal volume or level[edit]

  • Faders– The process of attenuating (lowering) the level of a signal. This is by far the most basic audio process, appearing on virtually every effect unit and mixer.[12]: 177 Utilizing controlled fades is the most basic step of audio mi xing, allowing more volume for prominent elements and less for secondary elements.
  • Boost – The process of amplifying a signal. Boosting is usually done using extremely slight amounts of amplification, enough to raise a signal without pushing it to the point of distortion. However, when using audio tape as opposed to recording on to a computer, sometimes a signal will be deliberately overdriven very hard to achieve an intense yet soft, 'rounded off' style of distortion known as tape saturation. Distortion fromclipping(overdriving) a digital signal will simply result in blasts of apparent white noise, and is almost universally regarded as unpalatable. Volume control units typically feature the ability to both boost and attenuate a signal.[12]: 177 
  • Panning– The process of altering the balance of an audio signal between the left and right channels of a stereo signal. The pan of a signal may be modified via a simple two-way pan control or anauto pannerthat continuously modulates and changes the pan of a signal.[1]: 49, 344 Panning is often used in the mi xing process toarrangethe track elements, simulating the placement of live bands.
  • Compressors– The process of reducing the dynamic range or difference between loudest and quietest parts of a signal. This is done by reducing the signal volume after a user-adjustable threshold is hit. The ratio of reduction to gain above the threshold is often also controllable, as well as the time it takes for reduction to activate (attack) or release. Most compressors will also have a makeup gain control, used to apply a boost after the gain reduction is replied to compensate for the quieter signal. Compression has many uses in the mi xing process, from evening out vocal volume to enhancing drums.[12]: 175 
  • Limiters– Using a compression ratio of 10:1 or higher is known as limiting- instead of applying gentle reduction to audio above the threshold, limiters forciblyflattenit down, allowing no signal above the threshold. Many limiting units also have built-in compressors that reduce the amount of audio actually passing the threshold. Many limiters also use digital algorithms tosoftenthe harsh sound of limited audio, morphing the wave instead of completely decapitating it (by removing part of the waveform entirely, intense distortion and vastly altered tones can occur.) Softer limiters are used with generous amounts of compression to create a more consistently loud track with less volume fluctuation, and harder limiters can be used as distortion effects or emergency safeties to protect large speaker systems from blowing out. Many analog amplifiers are fitted with their own basic limiters to prevent the high-voltage circuitry from overloading and blowing out.[12]: 176 
  • Dynamic expansion – Expansion[12]: 176 Dynamic expansion is essentially compression with an inverted threshold- any signal below a certain threshold is dynamically reduced while signals above the threshold remain untouched. Expansion is most commonly used to give volume to certain elements of recordings- e.g. the bass drum and snare drum. Expanders can also be set up so that when a signal drops below a set threshold, it will reduce gain until the output signal is forced below a certain level, and continue to hold the gain at that level until the input rises above the threshold. This application of expansion is called gating.

Processes that affect frequencies[edit]

The frequency response of a signal represents the amount (volume) of every frequency in the humanhearing range,consisting of (on average) frequencies from 20 Hz to 20,000 Hz (20 kHz.) There are a variety of processes commonly used to edit frequency response in various ways.

  • Equalization– Equalization is a broad term for any device that can alter parts of a signal frequency response. Some EQs use a grid of faders or knobs which can be arranged to shape each frequency, whereas others use bands that can target and subsequently boost or cut selectable series of frequencies.

[12]: 178 

  • Filters– Filters attenuate part of the audio spectrum. There are various types of filters. Ahigh-pass filter(low-cut) is used to remove unneeded bass from a sound source. Alow-pass filter(high-cut) is used to remove unneeded treble. These are most often used as a way todecluttera given mix to improve the clarity of the individual elements. Aband-pass filteris a combination of high- and low-pass filters, also known as a telephone filter (because a sound lacking in high and low frequencies resembles the quality of sound over a telephone).[13]

Processes that affect time[edit]

  • Reverbs– Reverbs are used to simulate acoustic reflections in a real room, adding a sense of space and depth to otherwisedryrecordings. Another use is to distinguish among auditory objects; all sound having one reverberant character will be categorized together by human hearing in a process calledauditory streaming.This is an important technique in creating the illusion of layered sound from in front of the speaker to behind it.[12]: 181 Before the advent of electronic reverb and echo processing, physical means were used to generate the effects. Anecho chamber,a large reverberant room, could be equipped with a speaker and microphones. Signals were then sent to the speaker and the reverberation generated in the room was picked up by the two microphones.[13]

Processes that affect space[edit]

  • Panning– While panning is aprocess that affects levels,it also can be considered a process that affects space since it is used to give the impression of a source coming from a particular direction. Panning allows the engineer to place the sound within thestereoorsurroundfield, giving the illusion of a sound's origin having a physical position.[1]
  • Pseudostereocreates a stereo-like sound image from monophonic sources. This way theapparent source widthor the degree oflistener envelopmentis increased. A number of pseudostereo recording and mi xing techniques are known from the viewpoint of audio engineers[14][15]and researchers.[16][17]

Downmi xing[edit]

The mixdown process converts a program with a multiple-channel configuration into a program with fewer channels. Common examples include downmi xing from5.1 surround soundto stereo,[a]and stereo to mono. Because these are common scenarios, it is common practice to verify the sound of such downmixes during the production process to ensure stereo and mono compatibility.

The alternative channel configuration can be explicitly authored during the production process with multiple channel configurations provided for distribution. For example, onDVD-AudioorSuper Audio CD,a separate stereo mix can be included along with the surround mix.[18]Alternatively, the program can be automatically downmixed by the end consumer's audio system. For example, aDVD playerorsound cardmay downmix asurround soundprogram to stereo for playback through two speakers.[19][20]

Mi xing in surround sound[edit]

Any console with a sufficient number of mix busses can be used to create a5.1 surround soundmix, but this may be frustrating if the console is not specifically designed to facilitate signal routing, panning, and processing in asurround soundenvironment. Whether working in an analog hardware, digital hardware, orDAWmi xing environment, the ability to pan mono or stereo sources and place effects in the 5.1 soundscape and monitor multiple output formats without difficulty can make the difference between a successful or compromised mix.[21]Mi xing in surround is very similar to mi xing in stereo except that there are more speakers, placed tosurroundthe listener. In addition to the horizontal panoramic options available in stereo, mi xing in surround lets themix engineerpan sources within a much wider and more enveloping environment. In a surround mix, sounds can appear to originate from many more or almost any direction depending on the number of speakers used, their placement and how audio is processed.

There are two common ways to approach mi xing in surround. Naturally, these approaches can be combined in any way themix engineersees fit.

  • Expanded Stereo– With this approach, the mix will still sound very much like an ordinary stereo mix. Most of the sources, such as the instruments of a band, backing vocals, and so on, are panned between the left and right speakers.[b]Lead sources such as the main vocal are sent to thecenter speaker.Additionally, reverb and delay effects will often be sent to the rear speakers to create a more realistic sense of being in an acoustic space. For the case of mi xing a live recording that was performed in front of an audience, signals recorded by microphones aimed at, or placed among the audience are sent to the rear speakers to make the listener feel as if they are a part of the audience.
  • Complete Surround/All speakers treated equally– Instead of following the traditional ways of mi xing in stereo, this much more liberal approach lets themix engineerdo anything they want. Instruments can appear to originate from anywhere, or even spin around the listener. When done appropriately and with taste, interesting sonic experiences can be achieved.

Recently, a third approach to mi xing in surround was developed by surroundmix engineerUnne Liljeblad.

  • Multi Stereo Surround (MSS)[22]– This approach treats the speakers in a surround sound system as a multitude of stereo pairs. For example, a stereo recording of a piano, created using two microphones in anORTF configuration,might have its left channel sent to the left-rear speaker and its right channel sent to the center speaker. The piano might also be sent to a reverb having its left and right outputs sent to the left-front speaker and right-rear speaker, respectively. Thus, multiple clean stereo recordings surround the listener without the smearing comb-filtering effects that often occur when the same or similar sources are sent to multiple speakers.

Mi xing in 3D sound[edit]

An extension to surround sound is 3D sound, used by formats such asDolby Atmos.Known asobject-basedsound, this enables additional speakers to represent height channels, with as many as 64 unique speaker feeds.[23][24]This has application in concert recordings, movies and videogames, and nightclub events.[25]

See also[edit]

Notes[edit]

  1. ^The left and right surround channels are blended with the left and right front channels. The center channel is blended equally with the left and right channels. The LFE channel is either mixed with the front signals or not used.
  2. ^Lower levels of these sources may also be sent to the rear speakers in order to create a wider stereo image.

References[edit]

  1. ^abcHuber, David Miles; Runstein, Robert E. (2001).Modern recording techniques(5th ed.). Focal Press.ISBN0-240-80456-2.
  2. ^Strong, Jeff (2009).Home Recording For Musicians For Dummies(Third ed.). Indianapolis, Indiana: Wiley Publishing, Inc. p. 249.
  3. ^Hepworth-Sawyrr, Russ (2009).From Demo to Delivery. The production process.Oxford, United Kingdom: Focal Press. p. 109.
  4. ^Rumsey, Francis; McCormick, Tim (2009).Sound and Recording(6th ed.). Oxford, United Kingdom: Elsevier Inc. p.168.ISBN978-0-240-52163-3.
  5. ^Rumsey, Francis; McCormick, Tim (2009).Sound and Recording(6th ed.). Oxford, United Kingdom: Elsevier Inc. p.169.ISBN978-0-240-52163-3.
  6. ^Huber, David Miles (2001).Modern Recording Techniques.Focal Press. p.321.ISBN978-0240804569.
  7. ^"The emergence of multitrack recording".RetrievedJune 17,2018.
  8. ^Eurythmics Biography.Musicianguide
  9. ^"Studio Recording Software: Personal And Project Audio Adventures".studiorecordingsoftware101. 2008. Archived fromthe originalon February 8, 2011.RetrievedMarch 20,2010.
  10. ^abWhite, Paul (2003).Creative Recording(2nd ed.). Sanctuary Publishing. p.335.ISBN978-1-86074-456-3.
  11. ^Izhaki, Roey (2008).Mi xing Audio.Focal Press. p. 566.ISBN978-0-240-52068-1.
  12. ^abcdefghiHolman, Tomlinson (2010).Sound for Film and Television(3rd ed.). Oxford, United Kingdom: Elsevier Inc.ISBN978-0-240-81330-1.
  13. ^abRumsey, Francis; McCormick, Tim (2009).Sound and Recording(6th ed.). Oxford, United Kingdom: Elsevier Inc. p.390.ISBN978-0-240-52163-3.
  14. ^Levinit, Daniel J. (2004). "Instrument (and vocal) recording tips and tricks". In Greenbaum, Ken; Barzel, Ronen (eds.).Audio Anecdotes.Natick: A K Peters. pp. 147–158.
  15. ^Cabrera, Andrés (2011)."Pseudo-Stereo Techniques. Csound Implementations".CSound Journal.2011(14): Paper number 3.Retrieved1 June2018.
  16. ^Faller, Christof (2005).Pseudostereophony Revisited(PDF).Audio Engineering Society Convention 118.Barcelona.Retrieved1 June2018.
  17. ^Ziemer, Tim (2017). "Source Width in Music Production. Methods in Stereo, Ambisonics, and Wave Field Synthesis". In Schneider, Albrecht (ed.).Studies in Musical Acoustics and Psychoacoustics.Current Research in Systematic Musicology. Vol. 4. Cham: Springer. pp. 299–340.doi:10.1007/978-3-319-47292-8_10.ISBN978-3-319-47292-8.
  18. ^Bartlett, Bruce; Bartlett, Jenny (2009).Practical Recording Techniques(5th ed.). Oxford, United Kingdom: Focal Press. p.484.ISBN978-0-240-81144-4.
  19. ^"What Is Downmi xing? Part 1: Stereo (LoRo)".TVTechnology.6 March 2007.
  20. ^Thornton, Mike."Podcast Follow Up - Surround Mixdown Formats".Pro Tools Expert.
  21. ^Huber, David Miles; Runstein, Robert (2010).Modern Recording Techniques(7th ed.). Oxford, United Kingdom: Focal Press. p.559.ISBN978-0-240-81069-0.
  22. ^"Surround Sound Mi xing".mix-engineer.Retrieved2010-01-12.
  23. ^"Dolby Atmos for Home".dolby.
  24. ^Hidalgo, Jason (April 26, 2012)."Dolby's Atmos technology gives new meaning to surround sound, death from above".Engadget.Retrieved2012-06-01.
  25. ^Authoring for Dolby Atmos Cinema Sound Manual(PDF)(Third ed.). Dolby Laboratories, Inc. 2014. pp. 69–103. Archived fromthe original(PDF)on 10 July 2015.Retrieved7 December2014.

External links[edit]

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