Mastering is the final step of audio post-production - it is the process of polishing your raw recording into a dynamic, loud and high quality professionally sounding audio product.
One of the main benefits of mastering is allowing your recording to sound good on a wide array of speakers, not just your personal setup. Your initial recording might sound great on your home setup, but when you play it elsewhere it may sound too quiet, muddy, bass heavy or harsh. It is worth taking your raw recording and listening to this on other speaker setups before doing anything further and making notes on how it sounds compared to other music you feel is of a high standard (such as professional albums).
This process is perhaps one of the hardest areas to get right in the audio engineering world, and is always wise to leave to professionals or friends who may have done this before. However, there are a few basics that will help get your mix sounding good and the more you do, the better you will get.
Mastering Recorded Vinyl, Edits & Tracks
If you have recorded individual tracks rather than an entire mix but feel that the overall 'loudness' of your recordings is quieter than purchased digital music, you may need to master these tracks.
You will have to do this process one track at a time if you want to do it well. If you are recording vinyl records, it can be worth while setting up your recording program with a mastering chain that corrects the recording as you go, rather than afterwards.
You can also set up a basic Mastering preset in your audio software, as most of the time you may only need to tweak small changes between different recordings.
The same approach can be taken if when making edits/bootlegs or producing your own tracks. This will give your tracks a bit more oomph. However, in order to take your own tracks to the next level, we strongly encourage you to approach a professional or friend experienced in mastering to get your tracks sounding more dynamic, polished and professionally sounding.
TIP: If you're on a tight budget, try LANDR. Developed over 8 years of research, LANDR uses A.I. and machine learning (think self-driving cars and Shazam), to replicate the processes human engineers make when mastering a track.
Mastering DJ Mixes
One thing that tends to let down aspiring DJs is the overall sound quality of their mix rather than their actual skills. You will need to pay close attention to how each track sits in the overall mix, how the tracks flow into each other and how the entire mix feel sounds. Sometimes you may need to change the volume of the mix.
NOTE: If you have pushed all of your tracks into the red when recording and there is considerable distortion it is best to re-record this rather than try to fix it with mastering. This is also true of recordings with low quality audio files. You are unable to clean up or fix a badly recorded mix. Rather, mastering allows you to enhance a good recording and tidy up any small errors.
Quality Control
It is a good idea to keep your recording at the highest recorded bit depth and frequency rate you can. You can always convert down later when you are ready. If you have recorded as a .WAV or .AIFF 24bit, keep the recorded audio like this for as long as possible. Do not render or convert down until the last step.
You should also make sure that at no stage of the mastering chain you redline or clip the audio signal. The point of mastering is to get things sounding full and loud without causing digital distortion.
Audio Editing
Audio Software
You can use audio editing software such as Ableton Live, Sony Soundforge, Logic or even free alternatives such as Audacity, although when using free software you will have limited editing options and the overall sound may not be as dynamic as you wish. In this article we will be using Ableton Live.
NOTE: Refer to your audio editing software manual for more information for anything you are unclear about.
Importing Audio
You will need to open a new project in your Audio Software. Once done, you will need to import the recorded onto a channel.
Cutting Your Audio
This is also where you will cut out any intro or outro silence or fade the mix out if you need to fit the audio onto a time-limited format like a compact disc
Firstly highlight the audio you wish to delete. This should normally be as simple as selecting the start and endpoints of the unwanted audio and pressing Delete.
Track Volume
You may need to change different parts of the recording's volume. This is especially important for DJ Mixes where one track may sound quieter or louder than the rest of the tracks when you listen to them again.
Make sure you give the overall mix a good few listens and make notes with pen and paper on where the mix could do with boosting, and where the mix could do with reducing. It is more important to use your ears than your eyes.
Most Audio Editing programs allow you to change the volume for different regions of the recording by editing Volume Automation over the recording (see the above image). This allows you to draw in adjustments to automation for volume, effects, panning or other parameters you may wish to change over the top of the waveform.
Effects and Processing (VST's)
Once you have imported and cut your audio, you may want to insert effects or processing software using plugins. The standard for professional audio is a VSTplugin. There are many different plugins around and most DAWs now come with some good quality VSTs so you won't need any extra software, although there are many top quality free and paid plugins specially designed for mastering that may give you better results.
Equalizing (EQ)
When it comes to recording a mix there is very little need to adjust the EQ settings. However if you feel that the entire mix has too much or too little low end or top end, or you have pushed the overall sound balance of the mix off due to an imbalance in your monitoring speakers when recording, you may need to do some basic EQing to get the mix sitting right.
When using EQ on a recorded mix, you will need to keep the following in mind:
- Set up the EQ on the master channel
- Choose the best quality EQ you have
- Select 'high quality' if there is the option
- Make sure you use a 'shelf' EQ (or a very wide 'Q' or band) as this will keep the feel of the all songs played - each track was (hopefully) mastered professionally once, and you should only be changing the overall balance of your mix.
- Don't use more than 1 or 2 dB of gain unless you know what you are doing. if it sounds very wrong, chances are you may need to start the recording process again.
- Don't boost any signal with the EQ, only reduce. (Use a limiter to increase the volume.)
- You should do any EQing before limiting.
- Make sure the audio isn't redlining or clipping.
Limiting (Compression)
The most common complaint about home recordings is that the volume is too quiet compared to professional CDs and the recording lacks 'punch'. Commercially released CDs go through a careful mastering process to get the loudest signal with the most dynamics.
However you can't just simply increase the volume, as any audio that exceeds zero dB in a digital environment starts to turn into digital distortion. All audio must be kept below this level in order to sound good.
You want to get the mix as close to zero as possible at most parts of the mix, without 'squashing' the dynamics of the tracks and limiting the audio too much and making the mix sound flat.
If you are not familiar with audio engineering the best way to limit your mix is to load a Limiter (or Compressor) VST plugin onto the Master channel and load a basic mix preset.
Note: A limiter is just a very extreme Compressor, and you will hear the terms sometimes swapped around.
Threshold
You will need to set the threshold of the Limiter / Compressor so that only the loudest peaks of the audio exceed the threshold, at which point these will be compressed (reduced in volume).
Unless you have gone over zero in the recording process (clipping or redlining) then your mix will be below zero.
You may find that you need to use a combination of adjusting the Volume curves (see above) and set a good Limiting threshold to get the best fullness of sound.
Compression Terminology
If you can't load a suitable preset, or want to learn more about compression, these are some basic compression terms:
- Threshold - this is the point at which the signal will start to be reduced. Be careful, the track may sound 'louder' when this is set low, but if you start to move this setting too far below the peak of the audio signal, you will start to squeeze out the dynamics of the track. The bulk of the sound should be under the threshold setting, you should only allow some of the peaks or transitions to go above this limit.
- Gain Reduction - this is the amount the compressor reduces the audio (this will change depending on your Threshold setting).
- Ratio - this is how much the audio is rolled off. Limiting is just very hard compression, with an infinite ratio, as such everything above the threshold will be reduced.
- Attack & release - how long before the compression starts and ends. For a mix CD, you want a short attack and long release so the compression/limiting is always on.
- 'RMS' or 'Peak' compression? Use 'peak' as it will find the true peak of the audio signal, not just calculate an average.
NOTE: Make sure your 'master' channel, is kept to -0.2dB or lower at peak value.
More reading:
http://en.wikipedia.org/wiki/Dynamic_range_compression
http://en.wikipedia.org/wiki/Audio_mastering
Monitoring Your Project
You should try to use good quality speakers when mastering. If at all possible, try to listen to the mix on good quality headphones too and other speakers until you are happy with the results.
You should also compare the original recording to the Mastered version as you progress (turn off the mastering plugins as you go). This will help you understand what you are doing to the sound. As long as you aren't squashing the dynamics out of the mix, and making it sound flat!
RENDERING & EXPORTING
When you have finished working on your master audio file and made all the adjustments you need, you will need to export your audio.
In most audio software you will need to highlight the entire mix, and then select 'Export Audio' or 'Render Audio'. This will apply any EQs, Compression or other plugins to the audio and save a new version of the mix to a location of your choosing.
NOTE: You may be asked to select the audio quality to render out - keep this file the same as your recording quality. Otherwise check the program's Preferences to set the quality.