Mixing and Mastering

Mixing

Mixing with Parametric EQ

Parametric EQ is different from a Graphic EQ as Graphic EQ uses faders to represent the various frequencies, whereas Parametric EQ is a ‘more digital’ approach, as it is a graph (X-axis is frequency range, Y-axis is dB + and -), on which you can drag a line around to shape the sound.

With either EQ, you can carry out 2 techniques: Corrective EQ means cutting unwanted frequencies and boosting desired frequencies. This is important for most mixes because it allows you to enhance the sound of desired frequencies as not being able to hear bad frequencies enhances the sound of the good frequencies. Creative EQ doesn’t stick to this principle, and is purely in aid of creating a unique sound. You simply cut and boost what you think sounds interesting.

EQ is arguably the most important mixing tool as, without ‘cutting the guff’, you leave space for unwanted sound, which will negatively impact the quality of the mix from the very beginning.

It is a good tool for starting with as it lets you ‘clean’ the sound and prepare it for effects, mastering and compression.

In a vast majority of situations, you would use EQ correctively, as there are not many types of music that opt for the use of these unwanted frequencies, whether they are certain frequencies in, for example, a voice that simply sounds bad or just general ‘room noise’.

If it wasn’t for EQ, then when making tracks and the whole master louder, these unwanted frequencies would be enhanced with the desired sound, which would make the quality of a track much lower.

Compressors and Advanced Compression Techniques

Compression is a technique in which a threshold is set (in dB), and the volume of any part of a track that passes that threshold is reduced, so that the volume of the whole track can be increased, without small peaks distorting/clipping it. It is important for making the sound of the track more even, subtly. The ratio feature is a measure of how much you want the sound to be reduced by. For example, a 2:1 ratio means that the sound that passes the threshold is half the volume above the threshold it previously was (twice as quiet) which is important when compressing a track on a mix because it can help you control how much a track is compressed by, as opposed to at what point the compression takes effect. The image below contains examples of when I used compression (the first of each stem is before compression, the second is after). As you can see, it is important to use this technique subtly, because if not, then the track becomes too even and dynamically dull, or not used enough which is useless.

Compression is an important technique as it allows you to make the track even, so that not only the occasional sound can be heard the most (like a kick drum, or slap bass, etc) and overall the volume can be increased. This technique is most important when dealing with tracks that have lots of individual clips, such as a track with a kick, snare or a bass where the musician plays the bass with slaps (which often create peaks). These instruments often create a short period of very loud noise (clips), which restricts the rest of the track in terms of how loud it can go, so it is more important to compress these, than tracks with fairly even/steady dynamic ranges.

If it wasn’t for compression, a track would be quiet except for the occasional sound which is extra loud, but can’t subtly be cut, and results in the volume of the track being incredibly uneven. For example, if you didn’t use compression on a track with a slap bass, the slaps would be so loud that the quieter parts of the track could not be turned up without the track clipping, and would be drowned out by the slapping, and by other instruments which can be turned up.

Using a Noise Gate

A noise gate affects sound opposite to the way a compressor does. A threshold is set, similarly to a compressor, but unlike a compressor, only sound that passes the threshold is heard. This is because desired sounds are often recorded louder (such as a vocalist singing into a mic), however, while recording, a vocalist might be breathing into the mic, moving their feet, and as always there is ‘room noise’. Using a noise gate means that the louder singing passes and is heard, but those unwanted sounds are completely cut. Using a noise gate can be difficult, as you have to determine exactly where the threshold should be, without cutting slightly quieter, desired sound, or letting louder, unwanted sound pass, or cutting in the middle of a word, just because it is sung a bit quieter.

A noise gate is absolutely not the MOST important processor in a mix, but is very useful for, like EQing, cutting unwanted sound with the goal of enhancing desired sound.

If it wasn’t for a noise gate, then the unwanted background sounds would be heard in the track, which could ruin the emotion and mood of the track.

Noise Gates are important to the quality of a lot of different types of recording. For example, a vocalist could be moving their feet slightly while recording, which may be very quiet, but will still be picked up by a sensitive condenser microphone. A bass or electric guitar amp may be buzzing very quietly. A pianist might be playing a piano with a squeaky pedal. These are all scenarios involving different instruments where a noise gate would be very useful. This is because it will cut (or greatly reduce, as dictated by the ‘Reduction’ feature) those unwanted noises which are quiet, but still audible.

The only limitation of a noise gate is that the mixing engineer has to be so precise with setting the threshold as, if the threshold is set too high, then desired sound will be cut, however, if it is set too low, undesired sound is let through, which would make the noise gate ineffective.

Effects Processing in the Mix

Effects differ from EQ, Compression and Noise Gates- these are ‘processors’. An effect is a creative way to make sound more interesting, such as reverb, echo, delay, flanging and overdrive. Effects are important as, without this ability, tracks would sound very dull, and the same as other tracks. It would also make the music sound very thin and weak.

Various effects do different things, but essentially their job is to simply add texture and substance to a sound and make it more interesting, which is important for ensuring a more powerful, substantial sound. The image below is an example of when I used effects. I created a bus to send the track through, with the effect/s added, and set to 100% ‘wet’ (meaning the bus channel has all affected audio) and the intensity of the effect is controlled by the bus’ fader, resulting in more control over it. The dry signal can then come through the original track and they can be balanced.

Effects are definitely not the most important part of a mix, but are very useful for making a sound more unique and interesting.

Without effects, audio could still be high quality, but would be very much the same as each other, and quite boring and dull.

Effects such as reverb and delay are most important to tracks such as vocals, as they make the vocals sound more as if they are actually in a room and makes them less dull/dry. An amp simulator and distortion/overdrive effects are important and very useful for guitars that have been recorded straight through a DI box, as it makes them sound less wiry and thin, and like they have actually been played through an amp, giving a realistic effect.

Reverb is the most commonly used effect (used on most, or even all, tracks), which arguably makes it the most important effect in a mix. This is because it immediately lifts a track, and makes it more spacious and gives it a sound as if it is in a real room, making it a very popular choice.

Monitoring Audio in the Mix

When recording music, I try to aim for a level of roughly -12dB. When mixing, I try to aim for roughly a peak level of -4.5dB.

You can monitor how loud frequencies are using tools like Voxengo SPAN, which is most important for letting you see the frequencies on the spectrum and how loud they are. This then allows you to shape them using various processors and effects. The general desired shape is higher at the bass, level/flat in the middle with a little boost at the high end.

Monitoring audio is one of the most important aspects of mixing, generally/ on all mixes, because unbalanced levels can sound incredibly unprofessional and can cause clipping.

Without audio monitoring, it creates unbalanced levels which can mean one instrument dominates the whole track, which sounds unprofessional and will draw attention away from the other instruments in the track.

Monitoring audio is most important when comparing the volume of different tracks. If one track is louder than the others then it will drown the others out, and it is all you will be able to hear. Monitoring audio is also important when ensuring that your mix doesn’t distort, which is why it is so important to ensure that a mix doesn’t peak above -3dB, as this can make it sound much worse quality and make mastering more difficult.

Mastering

Audio files need to be mastered for each track on an album for all of the following reasons:

One occasion when mastering is important is to make the song available on different formats. For example, when mastering a track to be cut onto vinyl, you have to use EQ to cut below 200 Hz on the left and right, or the needle jumps out of the groove.

Different formats have to be bounced as different sample rates and bit depths to accommodate how the format plays. For example, a CD is manufactured at 16 bit and 44.1 kHz.

Mastering is also important as it ensures that sound is even/level relative to all of the other tracks on an album, as it is unprofessional to have large, noticeable differences in the dynamics of the tracks.

However, the main reason mastering is so important is because it makes the sound of the track louder, and more powerful.

Mastering EQ Techniques

When mastering, a ‘Linear Phase EQ’ is used, which differs from a regular channel EQ, which is used when mixing. The main difference is that a Linear EQ is much more powerful, and is useful for the whole master, but unnecessarily powerful for individual mix channels. When EQing in both mastering and mixing, it is important to completely cut below (roughly) 25-30Hz, as most speakers cannot reach this low of a frequency, so it is unnecessary ‘guff’ that doesn’t need to be there. However, all other boosts and cuts made on a master track should be very subtle- no more than a 3-4dB cut or boost! You also use the EQ in a master to help correct the spectrum analyser, which shows which frequencies are most dominant.

EQ is arguably not THE most important part of a master, as its effect is very subtle and a lot of the ‘guff’ is cut when mixing, however it is still useful to ensure the highest quality master, as linear phase EQ is more powerful.

However, EQ is the most important for specific jobs, such as ‘cleaning sound’ (making it an important first step!). This means removing certain frequencies in a sound (for example, roughly 500 Hz in vocals) that simply sound bad, often like a ‘boing’/’wobble’ sound. Linear Phase EQ (the one used when mastering) is best for this because it is more powerful and has a stronger effect on the track (too powerful to be used on each channel on a mix).

The Linear Phase EQ can also be useful and important for helping to shape the Spectrum Analyser, as it is used to cut and boost certain frequencies (although, especially in the master, it is important to only make subtle cuts and boosts).

However the Linear Phase EQ, when used in a master, is not useful for specific instruments, as all of the tracks have been combined, so the EQing is much less precise and EQs the whole master.

If it wasn’t for the more powerful Linear EQ, then there may be unwanted room noise at certain frequencies, or the spectrum analyser may not show balanced frequencies, which would negatively affect the quality of the track.

Brickwall Limiter

A limiter is designed to ensure that sound levels do not pass a certain volume. In mastering, this level is usually set at -1dB. A brickwall limiter differs from a regular limiter as a regular limiter may let a little bit of sound over, but a brickwall limiter stops all of the sound. It is often better to use 2 limiters when mastering, as 2 limiters limiting subtly is more effective than 1, limiting more heavily. The first one can often have a threshold set at 0dB, as long as the last one is -1dB, as that is the maximum level for mastering because streaming and digital download sites usually compress to -1dB anyway.

The brickwall limiter is not the single most important processor in mastering, as all it really does is stop the level going over -1dB, however this is still a very important processor for tracks with lots of clipping and lots of peaks, as they are most like to try to pass the threshold and distort, so keeping levels below -1dB is important. Streaming sites compress tracks to this level anyway, so it will let you keep your master sound the way you want it to, without more compression affecting the track’s dynamic range. Besides this, it is also just pointless to master something with processors like compressors, for it to just be compressed again.

It is also important to keep levels to -1dB to stop the track from clipping, and potentially damaging any sound systems, or even people’s ears.

Brickwall limiters are most important if placed at the end of the mastering chain, as any processors added after could make sound go above -1dB (or whatever the output level is set to).

Master Bus Compression

Master bus compression is the multiband compressor, regular compressor and 2 limiters used on a master. All together, they ensure that the track peaks at -1dB, while being dynamically interesting, with not too many clips and peaks. The multiband compressor ‘fine-tunes’ compression in certain areas on the frequency spectrum, a general compressor does a little extra compression to support this, then the limiters stop the peak going above -1dB.

This is one of the most important parts of the master for the highest quality track, keeping dynamics interesting while stopping unwanted peaks, which allows you to make the whole track louder proportionally, or ‘using the space’, to put it another way.

If it wasn’t for the master bus compression, the master would be very uneven with random peaks and the rest of the track very quiet but unable to be made louder.

Master bus compression is most important to keep sound levels under control in a precise way. Multiband compressors are very important for much more precise compression, to help shape the spectrum analyser (such as Voxengo SPAN), because you can compress various frequency ranges. The regular compressor is important to make sure that the last bit of compression is added to the whole track, across all frequency ranges, to stop those extra few peaks from clipping. The 2 limiters are important for ensuring that peaks don’t go over -1dB so that the tracks are suitable for streaming sites, and match the levels of other tracks on the album.

Multiband Compression

Multiband compression is like a mix between an EQ and, obviously, a compressor. It uses the frequency spectrum layout, with a compressor for various, adjustable, frequency ranges. Like a compressor, it has a threshold, ratio, attack and release. These control the volume at which the compressor is activated, how much it compresses, when it ‘kicks in’ and when it stops, respectively. Usually, there are about 3+ sections on the bass, mid, and treble frequencies. This allows you to have much more control over what is compressed. The multiband compressor allows you to be much more precise in your compression than a regular compressor, however it is still a good idea to use both.

Multiband compressors are arguably one of the most important, useful processors due to its precision. It allows you to have such a large effect on a master and shape the sound on the spectrum analyser so precisely that it is very powerful and useful. As always, it is still important to be subtle with this processor, but it can still have a huge impact on a master.

Multiband compression is, like EQ, very important when shaping the frequency range to the ideal shape. It is also very important for songs where a certain frequency instrument causes clipping. For example, slap bass and kick drums typically cause a lot of clipping, and they also sit in the lower frequencies, so in a situation where these instruments are used, you might apply more compression to the lower band, so that the higher frequencies can remain less compressed.

If it wasn’t for the multiband compressor, then the master could still be compressed by the general compressor, but it would not be done as precisely, and any frequency ranges with worse clipping could be affected the same as frequencies with little/no clipping.

Enhancing Stereo Width

Stereo width means, as the name implies, how wide the music sounds, and how full and rich it is. This can be done in either/both the mix AND master. It can be achieved by panning (sending the signal left, right or central) tracks. To get the best effect with this, it is always best to have tiny variations in the 2 mono tracks that are panned, such as slight quantising (how closely the note fits the beat marking) differences and additional effects applied lightly to one side as, if the track is simply copied and pasted, it causes ‘phasing’, a phenomenon in which the exact same sound, played at the exact same pitch at the exact same time create the same sound and cancel each other out.

Enhancing stereo width is another technique which, like others, is not essential but improves the overall quality of a track. It is definitely not the most important part of mixing and mastering, but all good mixing and mastering engineers will do this.

If it wasn’t for enhancing stereo width, the sound would be much thinner and weaker. Some instruments may even be drowned out due to the lack of ‘space’. By enhancing the stereo width, you allow for more room for all instruments, and is used in most-all situations, as it is important for any time when stereo speakers can be used.

Enhancing stereo width is important for all masters. It gives the track more ‘air’ and allows all instruments to be heard more vividly. This can be achieved by using an enhancer, which pushes the sound out more to the side. This can also be achieved by panning, which sends signals left or right (used in mixing).

If it wasn’t for enhancing stereo width, then tracks would sound more muffled, and not as pleasing. Allowing more ‘space’ means that everything can be heard and is more clear.