Equlization at Professional mixing

There is a lot of different information about equalizers on the Internet. This information mainly refers to the technical aspect of the subject. But I would like to describe equalizers as one of the indispensable devices in edm mixing and mastering.
If we look at the whole process of music production, it will be obvious that using equalizers is appropriate at any production phase. These phases include the actual recording (writing the music material to an analog or digital storage device), mixing (turning a set of differently sounding instruments into an integral music piece), and mastering (bringing the mix to the final version that will be presented to the listeners).
The differences between these phases are obvious. During the first one equalizer is a part of the sound recording chain. Its influence is non-recurrent, so audio engineer can't cancel the changes made by the equalizer after recording is finished. The most common are the equalizers built into the preamp and the equalizers as individual units. The individual equalizers of high grade are very expensive, but such devices greatly improve the music quality.
For example, if a vocalist has a unique beautiful timbre, the equalizer can emphasize his voice colours. Alternatively, if some frequencies are missing, they can be added during recording with EQ. In that case, you can give the mixing studio a copy of the material, which is as close to your ideal as possible. When tuning a bass guitar or an acoustic guitar, musicians and sound engineers often have a chance to adjust the equalizer built into the preamp, guitar amplifier or guitar head. 

The choice depends on the genre of the future record. Different genres may require a different guitar sound, and the equalizer can make the same “guitar plus amplifier” pair suitable for stylistically dissimilar compositions.
During mixing and mastering equalization is performed very carefully, because usually at this point the main frequency pattern is already built by the instrument preprocessing. Technically, if a track is properly prepared, equalization might be avoided completely. However, it might be necessary to clean the side component of the track in the lower part. It will add some transparency to the sound when it will be played on different audio systems.
So, let’s find out what role does the equalizer play in the studio, what kinds of equalizers exist, what options do they have and which of these options are appropriate in different cases.
Types of equalizers
Let’s come down to essentials. As was already said, the equalizer is meant to alter a part of the spectrum of a particular instrument or voice, which makes it an indispensable device in any music studio. As a result of its work, the sound amplitude of the frequencies in a particular spectrum portion will become higher or lower.
The equalizer changes the sound amplitude (that is, its volume), so this device falls into the category of dynamic processors (we know that dynamics is the change of volume). All tools that somehow influence a part of the spectrum are usually referred to as filters.

On the one hand, the equalizer is a particular instance of a filter. On the other hand, filters can have slightly different parameters, so they belong to a different category of processing.
There are two types of equalizers: graphic and parametric.
Graphic equalizers
Nowadays graphic equalizers can be usually found in expensive cheap mixing and mastering services. They are also used during concert activity, when a multiband tuning of the audio chain is necessary. The simplest example of such a device is a panel with a set of sliders, each of which either increases or decreases the sound amplitude on a particular frequency.
Graphic equalizers have certain advantages. The main one is their simplicity and the possibility to simultaneously change completely different portions of spectrum in both directions. The usability and good visualization in graphic equalizers also make them useful. However, the drawbacks of these devices are substantial as well.
The main problem is the inability to precisely localize the frequency that needs to be affected. This disadvantage becomes even more significant due to an increasing demand for high quality. If a resonance appears on the frequency of 1.7 kHz, mixing engineer will have to adjust the nearest slider, which will be responsible for 1.6 kHz frequency. Of course, it’s an extremely rough tuning.
The second drawback is that the quality factor level is hard-set for every band (we’ll talk about the quality factor a little later). Some expensive models have an option of adjusting the quality factor, but most of the equalizers seen in mixing studios lack this function. 

And the third drawback (and a very important one) is that even if adjacent sliders are close to each other, it’s impossible to make the spectrum change perfectly smoothly. This characteristic of graphic equalizers causes contortions in the sound. They might not be perceptible in the live performances, but can be very significant during recording.
That’s why professional mixing studios usually avoid using graphic equalizers and choose parametric ones, which are more flexible and precise.
Parametric equalizers
Unlike graphic equalizers, parametric ones don’t have so many equalization bands. However, due to the ability of precise frequency localization, they have become a number one tool for mixing songs. Parametric equalizers usually have from one to four bands. Sometimes these bands are tied to a certain range and the band frequency can only be set in this range, but often all bands can be adjusted within full range. The name “parametric equalizers” was given to these devices because they have entirely modifiable equalization parameters. In the right hands, these tools can give a mixing engineer a great advantage in creating a musical pattern.
Use
Imagine that you need to pack two sounds with a similar spectrum in one mix and ensure that both of them are audible. In this case, reasonable equalization of each instrument will provide a separate space in the song for both of them.
Some frequency conflicts are solved by turning on High-pass and Low-pass filters, which also relates to equalization.
In some cases, an equalizer helps to remove timbral weakness of a voice or an instrument and adjust the influence of the room, standing waves or resonances on the sound.
All told, the equalizer has many usages in sound mixing studios. As any other instrument (yes, in relation to music the equalizer is exactly a musical instrument) it requires some skills and experience to work with to achieve result similar to our before after mixing mastering demos.