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

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. In the process of combining the separate tracks, their relative levels 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]

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
A simple mixing console

Main article: 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 and plugin-based processing

Outboard audio processing units (analog) and software-based audio plug-ins (digital) are used for each track or group to perform various processing techniques. 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 the "space" of the final audio wave; removing unnecessary frequencies and volume spikes to minimize the interference or "clashing" between each element.

Processes that affect signal volume or level

Processes that affect frequencies

The frequency response of a signal represents the amount (volume) of every frequency in the human hearing 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.

[12]: 178 

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,[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, 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 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.

Mixing in 3D sound

An extension to surround sound is 3D sound, used by formats such as Dolby Atmos. Known as "object-based" sound, 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]

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.

References

  1. ^ a b c Huber, David Miles; Runstein, Robert E. (2001). Modern recording techniques (5th ed.). Focal Press. ISBN 0-240-80456-2.
  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. ISBN 978-0-240-52163-3.
  5. ^ Rumsey, Francis; McCormick, Tim (2009). Sound and Recording (6th ed.). Oxford, United Kingdom: Elsevier Inc. p. 169. ISBN 978-0-240-52163-3.
  6. ^ Huber, David Miles (2001). Modern Recording Techniques. Focal Press. p. 321. ISBN 978-0240804569.
  7. ^ "The emergence of multitrack recording". Retrieved June 17, 2018.
  8. ^ "Eurythmics: Biography". Artist Directory. Rolling Stone. 2010. Retrieved March 20, 2010.[dead link]
  9. ^ "Studio Recording Software: Personal And Project Audio Adventures". studiorecordingsoftware101.com. 2008. Archived from the original on February 8, 2011. Retrieved March 20, 2010.
  10. ^ a b White, Paul (2003). Creative Recording (2nd ed.). Sanctuary Publishing. p. 335. ISBN 978-1-86074-456-3.
  11. ^ Izhaki, Roey (2008). Mixing Audio. Focal Press. p. 566. ISBN 978-0-240-52068-1.
  12. ^ a b c d e f g h i Holman, Tomlinson (2010). Sound for Film and Television (3rd ed.). Oxford, United Kingdom: Elsevier Inc. ISBN 978-0-240-81330-1.
  13. ^ a b Rumsey, Francis; McCormick, Tim (2009). Sound and Recording (6th ed.). Oxford, United Kingdom: Elsevier Inc. p. 390. ISBN 978-0-240-52163-3.
  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. Retrieved 1 June 2018.
  16. ^ Faller, Christof (2005). Pseudostereophony Revisited (PDF). Audio Engineering Society Convention 118. Barcelona. Retrieved 1 June 2018.
  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. 4. Cham: Springer. pp. 299–340. doi:10.1007/978-3-319-47292-8_10. ISBN 978-3-319-47292-8.
  18. ^ Bartlett, Bruce; Bartlett, Jenny (2009). Practical Recording Techniques (5th ed.). Oxford, United Kingdom: Focal Press. p. 484. ISBN 978-0-240-81144-4.
  19. ^ "What Is Downmixing? Part 1: Stereo (LoRo)". TVTechnology.
  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. ISBN 978-0-240-81069-0.
  22. ^ "Surround Sound Mixing". www.mix-engineer.com. Retrieved 2010-01-12.
  23. ^ "Dolby Atmos for Home". www.dolby.com.
  24. ^ Hidalgo, Jason (April 26, 2012). "Dolby's Atmos technology gives new meaning to surround sound, death from above". Engadget. Retrieved 2012-06-01.
  25. ^ Authoring for Dolby Atmos Cinema Sound Manual (PDF) (Third ed.). Dolby Laboratories, Inc. 2014. pp. 69–103. Retrieved 7 December 2014.