Audio equalization first came in to play in the 1920’s for radio broadcasting through the form of large chunky units with set frequency bands that could be adjusted to the broadcaster’s liking. At the time, the RCA 8B equalizer was the standard, which ended up being utilised by mixing engineers and music producers in the following couple decades.

In 1955, the Pultec EQP-1A was released, a unit that offered a similar effect, though with an increased amount of flexibility and a unique tone and subtle distortion that came from the amplifier in the system. This piece of equipment is still used today for its warm, musical sound and has been emulated my many plugin companies such as Waves and UAD (The UAD Pultec emulations are some of my most frequently used plugins, in fact).

Over the period of the 50s to the 70’s, it started to become common practice for equalizers to be built in to mixing desks, marking the start of an entirely new workflow that is still dominant in studio settings today. This ushered in the era of Neve and SSL equalizers that are also commonly sought after today for their unique tones and characteristics.

The next big leap in EQ technology was in the 70’s, when parametric EQ’s came in to fashion. These equalizers allowed for the ability to adjust the frequency bands with a precision previously unfathomable, allowing for precise, surgical corrective and creative usage. This is still an extremely common form of equalization for the flexibility it provides.

In the 1980’s, digital equalization became a new form of technology in the studio that was both more accessible to a wider audience as well as more flexible and clean than its predecessors. In the current day, digital EQ is the most common form of equalization due to its accessibility only increasing over time, as well as its capacity to recreate many different styles of EQ.

That being said, the older forms of equalization never died out, as each era and unit have their own unique characteristics that make them sought after to this day, with most mixing engineers either paying incredible amounts for older gear or using VST emulations of them in the DAW.

I feel that having an understanding of the history of EQ and what made each era and unit special has helped me to cater the types of EQ that I use for the type of sound I want for a song. For example, using the Pultec EQ on low end gives me a tone that I love when compared to a less characteristic digital EQ such as Fabfilter’s Pro-Q 3, however, if I were looking to attenuate a specific frequency that was poking out, the Pro-Q 3 would always be my go to due to its capacity for surgical equalization.

Sources:

https://blackroosteraudio.com/en/blogreader/a-brief-history-of-equalization

https://vintageking.com/blog/history-of-eq/?srsltid=AfmBOopvBdI8oTfsZtYw8uI07UMRfkEjMmPZRcMNaFaKYqaKSNRL_SIg

https://www.waves.com/9-eq-types-explained

Stereo sound can be traced back to developments made by EMI engineer ‘Alan Dower Blumlein’ in the 20th century. He patented his stereo sound technology in 1931, which involved the use of two grooves on records to create variations in amplitude of the stereo channels, as supposed to the previous dominant technology which only had one groove pattern that emitted a mono signal.

Stereo sound did not rise to become the dominant mode of audio production and listening until the 60’s due to the technology becoming more accessible to the general public. This process was encouraged by the use of stereo sound becoming standard in films, television and music, as well as the emerging popularity of other technologies such as tape machines and more elaborate mixing consoles and effects encouraging further experimentation with stereo sound.

By the 70’s and 80’s stereo was the standard for all devices, making space for further experimentation with what stereo sound could be. One such attempt was the quadraphonic sound system which involved 4 speakers in the corners of a space, however this did not take off due to its high costs and complex usage. One notable use of this technology was Pink Floyd’s ‘Dark Side of The Moon’, which was mixed in this format and performed live at Pompeii with this setup.

This technology did not go to waste, however, as it went on to influence the creation of the surround sound format as we know it, which is used predominantly in film but can be found in some more expensive home setups.

Currently, the emergence of spatial audio seems to me to be the next step forward in stereo sound and I am excited to see the technology become more accessible and fleshed out. In the future, experimenting more with different ways to mix and listen to music is something I want to explore, whether it be quadraphonic sound systems like Pink Floyd, spatial audio or any other technologies that will emerge.

Sources:

https://www.abbeyroad.com/news/the-history-of-recorded-music-has-its-roots-firmly-planted-at-no-3-abbey-road-2596

https://www.emiarchivetrust.org/alan-blumlein-and-the-invention-of-stereo/

Pictured is a visual representation of the stereo imaging for ‘Africa’ by D’angelo (including only the main instruments, not sounds that are only present for short moments of the track)

One interesting element of this song is that the vocals are further back in the mix than the drums and percussion, which is untypical for most commercial mixes. This is the case with many D’angelo tracks, as the rhythm tends to be in the driver’s seat with his music while the vocals serve more as an instrument than the centre of the track.

While it’s important to rely more on your ears than eyes while mixing, visual representations such as these can help in conceptualising depth and space in mixes. Considering where each instrument is coming from in the stereo field and how it interacts with the space around it is a core element of mixing, whether you are attempting to simulate the realism of a tight room or create ethereal soundscapes.

While creating a visual representation of every song you’re mixing and every reference track you use in the process may be unrealistic, taking the concept behind it in to your thought process when mixing can help to create more immersive listening experiences. For example, picturing the instruments as actually being played in a room and what that room looks, feels and sounds like, as well as who and where you are in that room, can help to create a sense of depth that is often forgotten; I believe that mixing in the box can make engineers lose sight of this as the process of staring at a flat, rigid DAW for hours can prevent you from hearing the instruments as part of the room, as supposed to the workflow of using analog gear that has you engaging with the space you are in more.

In mixing, a reference track is a song that shares similar qualities to the track being mixed that the engineer can use to assist them in the mixing process.

One reason that reference tracks are used is that having an industry standard point of comparison for a song that is being mixed can help to influence your decision making and allow you to assess where your mix may be falling short.

Another reason is that a reference track allows you to refresh your ears, as often times if you’ve been working on a mix for extended periods of time you can get used to the sound of the demo or work in progress and not notice that your mix may be, for example, much darker or brighter than what you had originally intended.

Additionally, sometimes engineers will use the demo of the song being mixed as a reference track to stop themselves from straying too far from the creative vision of the artist.

I make use of reference tracks when looking to be inspired by people who make bold mixing decisions, which can influence the way I think about the process and the risks I’m willing to take. One such example is Dijon, especially on his album ‘Absolutely’ and single ‘coogie’.

I also use reference tracks when there are songs that have specific elements to them that I love, such as the drum tone and separation of the elements of the mix in ‘Africa’ and the rest of the ‘Voodoo’ album by D’angelo.

I similarly use reference tracks when a song captures a specific emotion that I wish to convey in my own mix, such as the liberated and angelic feeling of ‘Set Your Spirit Free’ by Sault.