Audio mixing (recorded music)

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In sound recording and reproduction, audio mixing is the process of optimizing and combining multitrack recordings into a final mono, stereo or surround sound product. Audio mixing (recorded music)_sentence_0

In the process of combining the separate tracks, their relative levels (i.e. volumes) are adjusted and balanced and various processes such as equalization and compression are commonly applied to individual tracks, groups of tracks, and the overall mix. Audio mixing (recorded music)_sentence_1

In stereo and surround sound mixing, the placement of the tracks within the stereo (or surround) field are adjusted and balanced. Audio mixing (recorded music)_sentence_2

Audio mixing techniques and approaches vary widely and have a significant influence on the final product. Audio mixing (recorded music)_sentence_3

Audio mixing techniques largely depend on music genres and the quality of sound recordings involved. Audio mixing (recorded music)_sentence_4

The process is generally carried out by a mixing engineer, though sometimes the record producer or recording artist may assist. Audio mixing (recorded music)_sentence_5

After mixing, a mastering engineer prepares the final product for production. Audio mixing (recorded music)_sentence_6

Audio mixing may be performed on a mixing console or in a digital audio workstation. Audio mixing (recorded music)_sentence_7

History Audio mixing (recorded music)_section_0

In the late 19th century, Thomas Edison and Emile Berliner developed the first recording machines. Audio mixing (recorded music)_sentence_8

The recording and reproduction process itself was completely mechanical with little or no electrical parts. Audio mixing (recorded music)_sentence_9

Edison's phonograph cylinder system 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. Audio mixing (recorded music)_sentence_10

Emile Berliner's gramophone system recorded music by inscribing spiraling lateral cuts onto a vinyl disc. Audio mixing (recorded music)_sentence_11

Electronic recording became more widely used during the 1920s. Audio mixing (recorded music)_sentence_12

It was based on the principles of electromagnetic transduction. Audio mixing (recorded music)_sentence_13

The possibility for a microphone to be connected remotely to a recording machine meant that microphones could be positioned in more suitable places. Audio mixing (recorded music)_sentence_14

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. Audio mixing (recorded music)_sentence_15

Before the introduction of multitrack recording, all sounds and effects that were to be part of a record were mixed at one time during a live performance. Audio mixing (recorded music)_sentence_16

If the recorded mix wasn't satisfactory, or if one musician made a mistake, the selection had to be performed over until the desired balance and performance was obtained. Audio mixing (recorded music)_sentence_17

With the introduction of multi-track recording, the production of a modern recording changed into one that generally involves three stages: recording, overdubbing, and mixing. Audio mixing (recorded music)_sentence_18

Modern mixing emerged with the introduction of commercial multi-track tape machines, most notably when 8-track recorders were introduced during the 1960s. Audio mixing (recorded music)_sentence_19

The ability to record sounds into separate channels meant that combining and treating these sounds could be postponed to the mixing stage. Audio mixing (recorded music)_sentence_20

In the 1980s, home recording and mixing became more efficient. Audio mixing (recorded music)_sentence_21

The 4-track Portastudio was introduced in 1979. Audio mixing (recorded music)_sentence_22

Bruce Springsteen released the album Nebraska in 1982 using one. Audio mixing (recorded music)_sentence_23

The Eurythmics topped the charts in 1983 with the song "Sweet Dreams (Are Made of This)", recorded by band member Dave Stewart on a makeshift 8-track recorder. Audio mixing (recorded music)_sentence_24

In the mid-to-late 1990s, computers replaced tape-based recording for most home studios, with the Power Macintosh proving popular. Audio mixing (recorded music)_sentence_25

At the same time, digital audio workstations, first used in the mid-1980s, began to replace tape in many professional recording studios. Audio mixing (recorded music)_sentence_26

Equipment Audio mixing (recorded music)_section_1

Mixing consoles Audio mixing (recorded music)_section_2

Main article: Mixing console Audio mixing (recorded music)_sentence_27

A mixer (mixing console, mixing desk, mixing board, or software mixer) is the operational heart of the mixing process. Audio mixing (recorded music)_sentence_28

Mixers offer a multitude of inputs, each fed by a track from a multitrack recorder. Audio mixing (recorded music)_sentence_29

Mixers typically have 2 main outputs (in the case of two-channel stereo mixing) or 8 (in the case of surround). Audio mixing (recorded music)_sentence_30

Mixers offer three main functionalities. Audio mixing (recorded music)_sentence_31

Audio mixing (recorded music)_ordered_list_0

  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.Audio mixing (recorded music)_item_0_0
  2. Routing of source signals to internal buses or external processing units and effects.Audio mixing (recorded music)_item_0_1
  3. On-board processors with equalizers and compressors.Audio mixing (recorded music)_item_0_2

Mixing consoles can be large and intimidating due to the exceptional number of controls. Audio mixing (recorded music)_sentence_32

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. Audio mixing (recorded music)_sentence_33

The controls on a mixing console will typically fall into one of two categories: processing and configuration. Audio mixing (recorded music)_sentence_34

Processing controls are used to manipulate the sound. Audio mixing (recorded music)_sentence_35

These can vary in complexity, from simple level controls, to sophisticated outboard reverberation units. Audio mixing (recorded music)_sentence_36

Configuration controls deal with the signal routing from the input to the output of the console through the various processes. Audio mixing (recorded music)_sentence_37

Digital audio workstations (DAW) can perform many mixing features in addition to other processing. Audio mixing (recorded music)_sentence_38

An audio control surface gives a DAW the same user interface as a mixing console. Audio mixing (recorded music)_sentence_39

The distinction between a large console and a DAW equipped with a control surface is that a digital console will typically consist of dedicated digital signal processors for each channel. Audio mixing (recorded music)_sentence_40

DAWs can dynamically assign resources like digital audio signal processing power, but may run out if too many signal processes are in simultaneous use. Audio mixing (recorded music)_sentence_41

This overload can often be solved by increasing the capacity of the DAW. Audio mixing (recorded music)_sentence_42

Outboard and plugin-based processing Audio mixing (recorded music)_section_3

Outboard audio processing units (analog) and software-based audio plug-ins (digital) are used for each track or group to perform variousprocessing techniques. Audio mixing (recorded music)_sentence_43

These processes, such as equalization, compression, sidechaining, stereo imaging, and saturation are used to make each element as audible and sonically appealing as possible. Audio mixing (recorded music)_sentence_44

The mix engineer also will use such techniques to balance the "space" of the final audio wave; removing unnecessary frequencies and volume spikes to minimize the interference or "clashing" between each element. Audio mixing (recorded music)_sentence_45

Processes that affect signal volume or level Audio mixing (recorded music)_section_4

Audio mixing (recorded music)_unordered_list_1

  • 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. Utilizing controlled fades is the most basic step of audio mixing, allowing more volume for prominent elements and less for secondary elements.Audio mixing (recorded music)_item_1_3

Audio mixing (recorded music)_unordered_list_2

  • Boost – The process of adding volume to a signal. Boosting is done using extremely slight amounts of amplification, enough to raise a signal without pushing it over the limit of a pre-amplified signal. Some volume control units may feature the ability to both boost and attenuate a signal.Audio mixing (recorded music)_item_2_4

Audio mixing (recorded music)_unordered_list_3

  • 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 an "auto panner" that continuously modulates and changes the pan of a signal. Panning is often used in the mixing process to "arrange" the track elements, simulating the placement of live bands.Audio mixing (recorded music)_item_3_5

Audio mixing (recorded music)_unordered_list_4

  • Compressors – The process of reducing the dynamic range or difference between loudest and quietest parts of a signal. This is done with automatically controlled fader, which will reduce 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 apply a boost after the gain reduction is replied to compensate for the quieter signal. Compression has many uses in the mixing process, from evening out vocal volume to enhancing drums.Audio mixing (recorded music)_item_4_6

Audio mixing (recorded music)_unordered_list_5

  • Limiters – Limiting is essentially an extremely harsh form of compression- instead of applying gentle reduction to audio above the threshold, limiters forcibly "flatten" it 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 to "soften" the 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.Audio mixing (recorded music)_item_5_7

Audio mixing (recorded music)_unordered_list_6

  • Dynamic expansion – Expansion 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 and snare drums of a drum recording.Audio mixing (recorded music)_item_6_8

Audio mixing (recorded music)_unordered_list_7

  • Noise gating – When a signal drops below a set threshold, a gate 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.Audio mixing (recorded music)_item_7_9

Processes that affect frequencies Audio mixing (recorded music)_section_5

The frequency response of a signal represents the amount (volume) of every frequency in the human hearing range, consisting of (on average) frequencies from 20Hz to 20,000 Hz (20khz.) Audio mixing (recorded music)_sentence_46

There are a variety of processes commonly used to edit frequency response in various ways. Audio mixing (recorded music)_sentence_47

Audio mixing (recorded music)_unordered_list_8

  • 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.Audio mixing (recorded music)_item_8_10

Audio mixing (recorded music)_unordered_list_9

  • Filters – Filters are used to eliminate certain frequencies from the output. Filters strip off part of the audio spectrum. There are various types of filters. A high-pass filter (low-cut) is used to remove excessive room noise at low frequencies. A low-pass filter (high-cut) is used to help isolate a low-frequency instrument playing in a studio along with others. And a band-pass filter is 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).Audio mixing (recorded music)_item_9_11

Processes that affect time Audio mixing (recorded music)_section_6

Audio mixing (recorded music)_unordered_list_10

  • Reverbs – Reverbs are used to simulate acoustic reflections in a real room, adding a sense of space and depth to otherwise "dry" recordings. Another use is to distinguish among auditory objects; all sound having one reverberant character will be categorized together by human hearing in a process called auditory streaming. This is an important technique in creating the illusion of layered sound from in front of the speaker to behind it. Before the advent of electronic reverb and echo processing, physical means were used to generate the effects. An echo 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.Audio mixing (recorded music)_item_10_12

Processes that affect space Audio mixing (recorded music)_section_7

Audio mixing (recorded music)_unordered_list_11

  • Panning – While panning is a process 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 the stereo or surround field, giving the illusion of a sound's origin having a physical position.Audio mixing (recorded music)_item_11_13
  • Pseudostereo creates a stereo-like sound image from monophonic sources. This way the apparent source width or the degree of listener envelopment is increased. A number of pseudostereo recording and mixing techniques are known from the viewpoint of audio engineers and researchers.Audio mixing (recorded music)_item_11_14

Downmixing Audio mixing (recorded music)_section_8

The mixdown process converts a program with a multiple-channel configuration into a program with fewer channels. Audio mixing (recorded music)_sentence_48

Common examples include downmixing from 5.1 surround sound to stereo, and stereo to mono. Audio mixing (recorded music)_sentence_49

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. Audio mixing (recorded music)_sentence_50

The alternative channel configuration can be explicitly authored during the production process with multiple channel configurations provided for distribution. Audio mixing (recorded music)_sentence_51

For example, on DVD-Audio or Super Audio CD, a separate stereo mix can be included along with the surround mix. Audio mixing (recorded music)_sentence_52

Alternatively, the program can be automatically downmixed by the end consumer's audio system. Audio mixing (recorded music)_sentence_53

For example, a DVD player or sound card may downmix a surround sound program to stereo for playback through two speakers. Audio mixing (recorded music)_sentence_54

Mixing in surround sound Audio mixing (recorded music)_section_9

Any console with a sufficient number of mix busses can be used to create a 5.1 surround sound mix, but this may be frustrating if the console is not specifically designed to facilitate signal routing, panning and processing in a surround sound environment. Audio mixing (recorded music)_sentence_55

Whether working in an analog hardware, digital hardware, or DAW mixing 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. Audio mixing (recorded music)_sentence_56

Mixing in surround is very similar to mixing in stereo except that there are more speakers, placed to surround the listener. Audio mixing (recorded music)_sentence_57

In addition to the horizontal panoramic options available in stereo, mixing in surround lets the mix engineer pan sources within a much wider and more enveloping environment. Audio mixing (recorded music)_sentence_58

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. Audio mixing (recorded music)_sentence_59

There are two common ways to approach mixing in surround: Audio mixing (recorded music)_sentence_60

Audio mixing (recorded music)_unordered_list_12

  • 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. Lead sources such as the main vocal are sent to the center 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 mixing 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.Audio mixing (recorded music)_item_12_15
  • Complete Surround/All speakers treated equally – Instead of following the traditional ways of mixing in stereo, this much more liberal approach lets the mix engineer do anything he or she wants. 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.Audio mixing (recorded music)_item_12_16

Naturally, these two approaches can be combined in any way the mix engineer sees fit. Audio mixing (recorded music)_sentence_61

Recently, a third approach to mixing in surround was developed by surround mix engineer Unne Liljeblad. Audio mixing (recorded music)_sentence_62

Audio mixing (recorded music)_unordered_list_13

  • MSS – Multi Stereo Surround – 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 an ORTF 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. Additional elements of the song, such as an acoustic guitar recorded in stereo, might have its left and right channels sent to a different stereo pair such as the left-front speaker and the right-rear speaker with its reverb returning to yet another stereo pair, the left-rear speaker and the center speaker. 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.Audio mixing (recorded music)_item_13_17

Credits to the contents of this page go to the authors of the corresponding Wikipedia page: mixing (recorded music).