Fundamentals Of Mixing Music - Audio Mixing Techniques

Knowing the fundamentals of EQ and compression are paramount to achieving great mixes. This post is about audio mixing techniques covering aspects like how to make your sounds appear near or far using reverb and delay, how to use side chain compression and how to resolve frequency conflicts. Check out these tips and tricks and apply them in your music to instantly improve your mixes. 

BASIC SKILLS OF EQ 

Eliminate frequency conflicts between instruments. It is based on the non-linearity of human hearing. EQ must prevent acoustic masking unless desired. Problems of frequency conflict can be minimised by good arrangements, Example : Orchestra Music, Pop Music.

i) There is no universal equalizer. Every EQ sounds different.
Sometimes to get the same sound from two different EQs you may need to change the EQ settings drastically.
ii) The EQ works less with cutting frequency than boosting frequencies.
iii) In the bottom range, use small Q’s and in the top range use wide Q’s.
iv) Almost any change in one band will affect the change in other bands.v) When two similar frequencies with similar frequency range are played together, masking can occur. When one of the two instruments is lowered in volume by 12-15dB, it will disappear due to masking. However, panning can resolve these frequency conflicts due to spreading the stereo image hard left and right and solve frequency conflicts on instrument groups.

It is easier to divide the mix into different frequency
Broadly we can divide the mix into 3 parts :
a) 0Hz – 120Hz b) 120Hz – 8kHz  c) 8kHz – 22kHz

BASS AND KICK – CONFLICT - 1 AND SOLUTION :

CONFLICT -1 –The kick usually has a hump somewhere between 40Hz and 200Hz wherein hump is at root note of the Kick. Bass usually has a linear frequency range from 40Hz – 1500Hz. This implies that kick and bass have overlapped frequencies which need to be treated. Usually due to overlapping spectrums of kick and bass, the low frequency of kick drum disappears.

SOLUTION – To solve conflict 1, cut the fundamental frequency (hump) of the kick from the bass channel. Use only non-linear phase EQ. Cut 3-5dB this brings out the kick punch.


BASS AND KICK – CONFLICT - 2 AND SOLUTION :

CONFLICT -2 – If the click of the kick is very prominent, the presence of the bass gets masked but we want to make it sound more prominent in the mix without compromising the attack and punch of the kick.

SOLUTION – To solve conflict 2, use mid band saturation. Saturating the mid band ensures that the bass plays well even on small speakers. This is particularly useful for situations where the bass lacks mid energy and presence. However we must not overdo this as the bass may start to sound thin as we increase the mids in the bass using saturation. 

Side chain Compression And Kick Duration: Side chain compression is used to trigger the compression of an element when another plays. To apply side chain compression to kick and bass in a way that the bass gets compressed when the kick plays, all you need to do is side chain your kick to your bass.  

It’s important that the duration of the kick matches the tempo of the track. The kick should make a quarter note from the duration of one bar. Side chain compression can be used in EDM, Pop etc. and can be used not only with the bass but also with leads, guitars, pads etc. Reverb and delay can also be side-chained. 

Artificial Side Chain: This is a technique used to create extra groove and interest. Suppose kick and bass have side chain compression, we can add a closed Hi-Hat on all beats at low volume so that it creates a pumping effect without any real side chain applied.

BASS AND GUITARS:

Frequency conflict is below 500Hz. A Shelving filter (Low Shelf) can be used on the guitar track to shelve the lows out. Boost at around 4k and 8k can make the guitar sound brighter. It is possible to boost from 1.2k – 3kHz for sharpness. If a guitar sounds too acid, you can cut frequencies in this range.

SYNTHS, PADS, STRINGS:

Synths can have conflicts with all frequencies. Hence we must compare the sound with all Instruments separately like kick, bass, guitars, etc. Timbres of synths can be played in different octaves to balance out the frequency spectrum. Cut 400Hz in leads, 800Hz in pads and 1kHz in strings.

PERCUSSIONS  AND CYMBALS:

Use Shelving filter to cut out lows below 1kHz from all percussions and cymbals. Do not use ‘Low Cut’ filter as they may sound un-natural and thin.

SNARE DRUM:

The snare drum overlaps many frequency of other instruments. Low cut up to 100Hz or 120Hz to make space for the kick and bass. The classical 14” snare drum has almost linear frequency response with a hump at 200 – 300Hz. This resonance has to be Notched out to place it correctly in the mix.

 

COMPRESSION


i) Vocal compression: The vocal should not sound harsh/fatiguing to the ear but also must sound smooth, polished not raw/rough. If you want the compressor to act mostly on peaks, choose a threshold which will just touch on the peaks. Keep a fast attack (Not very fast though) and lowest release ~500ms. This will keep the sound within the compressor for most of the time and will slowly come out. You can use a ratio of 4:1 or more so that the compressor aggressively acts on the peaks that cross the threshold and remains inactive until the threshold.

ii) Ducking: Ducking is a compression technique used to duck one sound under the other so that one is more prominent and the other is not.
Example : If a synth lead and a vocal are fighting wherein
we want to push the lead behind the vocal, we can use ducking. Using this technique will make the synth lead slightly dull but this may be required in this scenario because everything cannot be equally bright and in the forefront of the mix. Only if there is contrast you can appreciate the bright and not so bright elements in the mix. For ducking, usually use a very fast attack ~0.5ms or less, release ~160ms, Ratio ~6:1, with threshold adjusted so that gain reduction ~6db. Ducking can be used well on background vocals. If used on lead vocals, although it brings the vocals out, it makes it slightly dull and not as bright due to the fact that the transients have been squished quite a bit and re-shaped.

iii) Limiting: Limiters can be used as the last plugin in the chain for the layer (vocals/drums/guitars etc.) for keeping the peaks in check. This makes it sound smoother. Overall it will help in louder masters. Allow only 1-2db of gain reduction here.

iv) Parallel Compression: In normal compression, we look at bringing the transients in control by bringing the loudest and softest parts to sound more uniform. This brings down the peaks. However, in parallel compression we are actually not touching the peaks, we are just bringing up the quieter sections, which tends to sounds more natural with more dynamics. It’s best to use it along with a layer of normal compression.

For this compressor use a very high ratio and crush it. Typical compressor settings would be like: Attack ~5-10ms, this brings some fullness and body to the sound. Release ~500-1000ms to avoid pumping. Must sound consistent. G.R ~10-12dB. Next use an EQ to de-mud at around 200 and 600Hz.

v) Multi-band Compression: Multi-band compression is basically frequency range specific compression so that we can compress the frequencies in the mix to different degrees. Compressor attack and release can act as an envelope shaper.

vi) Maximizers: Maximizers are generally peak limiters without normalization. Maximizers are suited for final mastering. For xxample: Good RMS Value of -11dBFS will result in transparent master if the mix is balanced. On the maximizer apply the same 11dB of Gain.

 

DRUMS:

To add a click to a kick, you can layer a low frequency kick with a high frequency kick or with a closed hi-hat. For a fat snare, you can add one short punchy sample for the highs and one slightly layer sample for warm release. You can also add a kick for the bass component. For a subby kick you can add a 50Hz sine wave underneath the kick to give it more subs. Use the pitch envelope for precision. To blend two kick textures it is also possible to blend two kick waveforms and cross-fade into one sample. This way we can use attack from one kick and release from another kick.


Maintaining mono compatibility even when stereo image is wide: If you have any Instrument like guitar/synth etc. use a double track and pan one hard left and one hard right. After that use slightly different processing on the left and right channels to give the stereo width. This will still retain mono compatibility (Unless difference between Left and Right is too much). For a synth, we can change parameters like filter, cut off and filter resonance, reverb time etc. You can direct different oscillators to different filters, change filter types etc.

Any difference between left and right will be perceived as widening but mono compatibility will be maintained. This can also be used for wide ‘stereo bass’ by playing with oscillator phase or oscillator start time. If oscillator phase is changed too much, it will lower the bass volume in mono.

NEAR AND FAR EFFECT: To situate an instrument in an imaginary room or create the near and far effect in space, these guidelines can be followed:


1) To make something sound far – Reduce the volume, Roll off high frequencies, make reflection sound louder than dry sound, use a reverb with long tail and release time, do not use stereo enhancer.


2) To make something sound near – Use a stereo enhancer. Make sure the reverb is panned wide, reverb is bright, short and dry and use a short delay which must be panned wide. The further the source of sound, the less high frequency we hear from it. To simulate approach of source, we shelve out low frequency and add brightness and sparkle for achieving the ‘near’ effect.

This is how we can show depth with EQ.

 

REVERB

In every reverb, we should use ‘damping’. This makes the reverb less artificial. Cut high frequencies before they pass through a Reverb or simply EQ your reverb to taste. Use true Stereo Reverb as per the desired position of the instrument in space.

There are two modes of sends on effects – pre and post fader. In pre-fader mode the volume of sends does not depend on fader’s level, so it is very comfortable to make an ambience. In post-fader mode it would be hard to make a reverb tail louder, but in pre-fader mode it can be done easily to give warmth in the reverb.

With stereo reverbs you can add a delay of 8-10ms on one channel of the reverb for width. Reverb can be used on all channels as a send to glue everything together.