Audio mixing (recorded music)

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Digital Mixing Console Sony DMX R-100 used in project studios Sony DMXR100.jpg
Digital Mixing Console Sony DMX R-100 used in project studios

In sound recording and reproduction, audio mixing is the process of combining multitrack recordings into a final mono, stereo or surround sound product. 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. In stereo and surround sound mixing, the placement of the tracks within the stereo (or surround) field are adjusted and balanced. [1] :11,325,468 Audio mixing techniques and approaches vary widely and have a significant influence on the final product. [2]

Contents

Audio mixing techniques largely depend on music genres and the quality of sound recordings involved. [3] The process is generally carried out by a mixing engineer, though sometimes the record producer or recording artist may assist. After mixing, a mastering engineer prepares the final product for production.

Audio mixing may be performed on a mixing console or in a digital audio workstation.

History

In the late 19th century, Thomas Edison and Emile Berliner developed the first recording machines. The recording and reproduction process itself was completely mechanical with little or no electrical parts. 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. 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 electromagnetic transduction. 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 of multitrack recording, all sounds and effects that were to be part of a record were mixed at one time during a live performance. 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. 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. [6]

Modern mixing emerged with the introduction of commercial multi-track tape machines, most notably when 8-track recorders were introduced during the 1960s. The ability to record sounds into separate channels meant that combining and treating these sounds could be postponed to the mixing stage. [7]

In the 1980s, home recording and mixing became more efficient. The 4-track Portastudio was introduced in 1979. Bruce Springsteen released the album Nebraska in 1982 using one. 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. [8] In the mid-to-late 1990s, computers replaced tape-based recording for most home studios, with the Power Macintosh proving popular. [9] At the same time, digital audio workstations, first used in the mid-1980s, began to replace tape in many professional recording studios.

Equipment

Mixing consoles

A simple mixing console Mixing Console Discom2.jpg
A simple mixing console

A mixer (mixing console, mixing desk, mixing board, or software mixer) is the operational heart of the mixing 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 mixing) 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.

Mixing 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 mixing 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 mixing features in addition to other processing. An audio control surface gives a DAW the same user interface as a mixing console. 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. DAWs can dynamically assign resources like digital audio signal processing power, but may run out if too many signal processes are in simultaneous use. This overload can often be solved by increasing the capacity of the DAW. [12]

Outboard gear and plugins

Outboard gear (analog) and audio plug-ins (digital) can be inserted into the signal path to extend processing possibilities. Outboard gear and plugins fall into two main categories: [10] [11]

Multiple level controls in signal path

A single signal can pass through a large number of level controls, e.g. individual channel fader, subgroup master fader, master fader and monitor volume control. According to audio engineer Tomlinson Holman, problems are created due to the multiplicity of the controls. Each and every console has their own dynamic range and it is important to utilize the controls correctly to avoid excessive noise or distortions. [12] :174

Processes that affect levels

Processes that affect frequency response

There are two principle frequency response processes:

Processes that affect time

Processes that affect space

Downmixing

The mixdown process converts a program with a multiple-channel configuration into a program with fewer channels. Common examples include downmixing from 5.1 surround sound to stereo, [lower-alpha 1] 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, on DVD-Audio or Super 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, a DVD player or sound card may downmix a surround sound program to stereo for playback through two speakers. [19] [20]

Mixing in surround sound

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. 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. [21] Mixing in surround is very similar to mixing in stereo except that there are more speakers, placed to surround the listener. 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. 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 mixing in surround:

Naturally, these two approaches can be combined in any way the mix engineer sees fit. Recently, a third approach to mixing in surround was developed by surround mix engineer Unne Liljeblad.

Notes

  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.

Related Research Articles

Mixing console Device used for audio mixing

In sound recording and reproduction, and sound reinforcement systems, a mixing console is an electronic device for combining sounds of many different audio signals. Inputs to the console include microphones being used by singers and for picking up acoustic instruments, signals from electric or electronic instruments, or recorded music. Depending on the type, a mixer is able to control analog or digital signals. The modified signals are summed to produce the combined output signals, which can then be broadcast, amplified through a sound reinforcement system or recorded.

Recording studio facility for sound recording

A recording studio is a specialized facility for sound recording, mixing, and audio production of instrumental or vocal musical performances, spoken words, and other sounds. They range in size from a small in-home project studio large enough to record a single singer-guitarist, to a large building with space for a full orchestra of 100 or more musicians. Ideally both the recording and monitoring spaces are specially designed by an acoustician or audio engineer to achieve optimum acoustic properties.

Surround sound more than two channels, with loud speakers in the front, back and sides

Surround sound is a technique for enriching the fidelity and depth of sound reproduction by using multiple audio channels from speakers that surround the listener. Its first application was in movie theaters. Prior to surround sound, theater sound systems commonly had three "screen channels" of sound that played from three loudspeakers located in front of the audience. Surround sound adds one or more channels from loudspeakers to the side or behind the listener that are able to create the sensation of sound coming from any horizontal direction around the listener.

Reason (software) Software for creating and editing music

Reason is a digital audio workstation for creating and editing music and audio developed by Swedish software company Reason Studios. Reason emulates a rack of hardware synthesizers, samplers, signal processors, sequencers, and mixers, all of which can be freely interconnected in an arbitrary manner. Reason can be used either as a complete virtual music studio or as a set of virtual instruments to be used with other sequencing software in a fashion that mimics live performance.

DI unit Audio signal conversion device

A DI unit is an electronic device typically used in recording studios and in sound reinforcement systems to connect a high-output impedance, line level, unbalanced output signal to a low-impedance, microphone level, balanced input, usually via an XLR connector and XLR cable. DIs are frequently used to connect an electric guitar or electric bass to a mixing console's microphone input jack. The DI performs level matching, balancing, and either active buffering or passive impedance matching/impedance bridging to minimize unwanted noise, distortion, and ground loops. DI units are typically metal boxes with input and output jacks and, for more expensive units, “ground lift” and attenuator switches.

Digital audio workstation Computer workstation or software application used for creating music or editing audio

A digital audio workstation (DAW) is an electronic device or application software used for recording, editing and producing audio files. DAWs come in a wide variety of configurations from a single software program on a laptop, to an integrated stand-alone unit, all the way to a highly complex configuration of numerous components controlled by a central computer. Regardless of configuration, modern DAWs have a central interface that allows the user to alter and mix multiple recordings and tracks into a final produced piece.

Sound reinforcement system Amplification sound system for public events

A sound reinforcement system is the combination of microphones, signal processors, amplifiers, and loudspeakers in enclosures all controlled by a mixing console that makes live or pre-recorded sounds louder and may also distribute those sounds to a larger or more distant audience. In many situations, a sound reinforcement system is also used to enhance or alter the sound of the sources on the stage, typically by using electronic effects, such as reverb, as opposed to simply amplifying the sources unaltered.

Neve Electronics was a manufacturer of music recording and broadcast mixing consoles and hardware. It was founded in 1961 by Rupert Neve, the man credited with creating the modern mixing console.

Aux-send

An aux-send is an electronic signal-routing output used on multi-channel sound mixing consoles used in recording and broadcasting settings and on PA system amplifier-mixers used in music concerts. The signal from the auxiliary send is often routed through outboard audio processing effects units and then returned to the mixer using an auxiliary return input jack, thus creating an effects loop. This allows effects to be added to an audio source or channel within the mixing console. Another common use of the aux send mix is to create monitor mixes for the onstage performers' monitor speakers or in-ear monitors. The aux send's monitor mix is usually different from the front of house mix the audience is hearing.

Panning is the distribution of a sound signal into a new stereo or multi-channel sound field determined by a pan control setting. A typical physical recording console has a pan control for each incoming source channel. A pan control or pan pot is an analog control with a position indicator which can range continuously from the 7 o'clock when fully left to the 5 o'clock position fully right. Audio mixing software replaces pan pots with on-screen virtual knobs or sliders which function like their physical counterparts.

Re-amping is a process often used in multitrack recording in which a recorded signal is routed back out of the editing environment and run through external processing using effects units and then into a guitar amplifier and a guitar speaker cabinet or a reverb chamber. Originally, the technique was used mostly for electric guitars: it facilitates a separation of guitar playing from guitar amplifier processing—a previously recorded audio program is played back and re-recorded at a later time for the purpose of adding effects, ambiance such as reverb or echo, and the tone shaping imbued by certain amps and cabinets. The technique has since evolved over the 2000s to include many other applications. Re-amping can also be applied to other instruments and program, such as recorded drums, synthesizers, and virtual instruments.

Parallel compression, also known as New York compression, is a dynamic range compression technique used in sound recording and mixing. Parallel compression, a form of upward compression, is achieved by mixing an unprocessed 'dry', or lightly compressed signal with a heavily compressed version of the same signal. Rather than bringing down the highest peaks for the purpose of dynamic range reduction, it reduces the dynamic range by bringing up the softest sounds, adding audible detail. It is most often used on stereo percussion buses in recording and mixdown, on electric bass, and on vocals in recording mixes and live concert mixes.

An audio signal is a representation of sound, typically using either a level of electrical voltage for analog signals, or a series of binary numbers for digital signals. Audio signals have frequencies in the audio frequency range of roughly 20 to 20,000 Hz, which corresponds to the lower and upper limits of human hearing. Audio signals may be synthesized directly, or may originate at a transducer such as a microphone, musical instrument pickup, phonograph cartridge, or tape head. Loudspeakers or headphones convert an electrical audio signal back into sound.

Ambiophonics is a method in the public domain that employs digital signal processing (DSP) and two loudspeakers directly in front of the listener in order to improve reproduction of stereophonic and 5.1 surround sound for music, movies, and games in home theaters, gaming PCs, workstations, or studio monitoring applications. First implemented using mechanical means in 1986, today a number of hardware and VST plug-in makers offer Ambiophonic DSP. Ambiophonics eliminates crosstalk inherent in the conventional “stereo triangle” speaker placement, and thereby generates a speaker-binaural soundfield that emulates headphone-binaural sound, and creates for the listener improved perception of “reality” of recorded auditory scenes. A second speaker pair can be added in back in order to enable 360° surround sound reproduction. Additional surround speakers may be used for hall ambience, including height, if desired.

Audio signal flow is the path an audio signal takes from source to output. The concept of audio signal flow is closely related to the concept of audio gain staging; each component in the signal flow can be thought of as a gain stage.

Harrison Mixbus is a digital audio workstation (DAW) available for Microsoft Windows, Mac OS X and Linux operating systems and version 1 was released in 2009.


A mixing engineer is responsible for combining ("mixing") different sonic elements of an auditory piece into a complete rendition, whether in music, film, or any other content of auditory nature. The finished piece, recorded or live, must achieve a good balance of properties, such as volume, pan positioning, and other effects, while resolving any arising frequency conflicts from various sound sources. These sound sources can comprise the different musical instruments or vocals in a band or orchestra, dialogue or foley in a film, and more.

Matrix mixer

A matrix mixer is an audio electronics device that routes multiple input audio signals to multiple outputs. It usually employs level controls such as potentiometers to determine how much of each input is going to each output, and it can incorporate simple on/off assignment buttons. The number of individual controls is at least the number of inputs multiplied by the number of outputs.

Professional audio store

A professional audio store is a retail business that sells, and in many cases rents, sound reinforcement system equipment and PA system components used in music concerts, live shows, dance parties and speaking events. This equipment typically includes microphones, power amplifiers, electronic effects units, speaker enclosures, monitor speakers, subwoofers and audio consoles (mixers). Some professional audio stores also sell sound recording equipment, DJ equipment, lighting equipment used in nightclubs and concerts and video equipment used in events, such as video projectors and screens. Some professional audio stores rent "backline" equipment used in rock and pop shows, such as stage pianos and bass amplifiers. While professional audio stores typically focus on selling new merchandise, some stores also sell used equipment, which is often the equipment that the company has previously rented out for shows and events.

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