If you type audio mastering into Google and hit enter you will find so many different definitions that it is no wonder some people sarcastically call it a dark art. Thing is, most artists (and a lot of people who call themselves “engineers”) don’t really understand the mastering stage of production. To a lot of people mastering is this mysterious endeavor that happens after mixing that finishes a song. But what does a mastering engineer actually do to a song? Let us shed some light on this mysterious endeavor.
What is Audio Mastering?
In a nutshell, mastering is the last stage of audio production and at the same time the first step in distribution. The mastering process prepares a song or a collection of songs for distribution by adjusting things like track length, distance between tracks on a CD, general frequency content, dynamic range, etc., and by producing the final stereo file for distribution – we will take a look at all the steps in detail. We will only be looking at native plug-ins and editing tools found in Pro Tools for this article but be aware that there are a ton of great mastering tools and plug-ins out there.
Listening and Reference Tracks
The first step in all mastering session must be thorough, repetitive listening. Take at least half an hour, though the more the better, and listen to each track your mastering project will include. It is important to try and listen to the mix as a whole and not focus on individual elements.
Think of the mix as a finished job and focus on the frequency content and dynamics of the whole mix. Jot down observations about things that you feel need some work – the high end, the low end, the dynamics of the song. After you finish, go through your record collection and find some songs that are similar in genre and feeling to the music you are working on and proceed to give them a very thorough listen as well. Try to find similarities and differences in frequency content and dynamic between your songs and the reference tracks.
Configuring Your Mastering Session
Import all the songs you will be working on into a Pro Tools session, each onto its own track and also add the reference tracks to the session, also on separate tracks.
Arrange them in such a way that it is easy to see each song next to its reference track and in order to facilitate workflow add some memory locations to key spots in the song you feel need more attention (the chorus, the bridge, etc. – you can add memory locations by hitting Enter on your keyboard). Do not forget to add a Master Fader to the session.
Tops & Tails
The next step to take is to adjust the beginning and the ending of the song so that you are happy with the amount of time the song takes to start at the amount it takes the song to stop playing after the song finishes. Cut any parts you deem unnecessary and using the selector and command + F / control + F shortcut open up the fade menu and create an appropriate fade in and fade out for your song so it does not start or end with a pop.
Set Up A Mastering Signal Processing Chain
You will instantiate plug-ins across every track in order to master your songs, but which ones should you use? The best way to go about it is deciding on some plug-ins and adding them to all the tracks and then if you feel one track need something special you can go ahead and look for that plug-in that does the trick.
I recommend starting practicing mastering with the EQ3 7-band, the Dyn3 Compressor/Limiter and Maxim. This is a very basic mastering chain that will help you get started with mastering. To instantiate these across all of your tracks (except the master fader of course) select all your songs and while clicking Option/ALT click on insert slot A on any track and choose EQ3 7-Band. Do the same for the other two plug-ins (with the next two insert slots) making sure that Maxim is inserted last in the chain.
Go back to your notes and see what kind of modifications you wanted to make to the frequency content of the songs. Use the EQ lightly – if you find yourself cutting or boosting more than 3 dB at any point, you are doing it wrong. The best way do it is make a small modification and the listen for a while – and keep going back and forth between your track and the reference track and compare the frequency content of the two.
An important thing is to turn down the volume of the reference track to match the volume of the track you are working on. The general tips to using EQ are valid in mastering as well – when boosting frequencies try to use wide bandwidths ( the Q parameter) and when cutting narrower values.
There are no specific things to do in a mastering session with EQ as all songs are different, even songs on the same album – listen a lot and keep trying to find problems, cluttered areas or spectrum areas that are too prominent in relation to the others. Don’t not be afraid to use shelves – a lot of times when I master I use a high shelve to boost all frequencies above 8 kHz and give myself a nice high boost.
If you are working on more than one song also go back and forth between the track you are currently working on and the others to listen to how frequency content differs from one song to the next – if the difference is too dramatic be careful to adjust it.
Video: EQ3-7 Band by AVID Controls Review
The compressor is the next tool in the chain and like the EQ, you should not use it too aggressively. Start from a simple setting: 50 ms Attack, 100 ms Release, a Ratio of 2:1, a Knee of about 12 and then start lowering the Threshold until you get around 1.5-3 dB gain reduction.
Listen closely to what that does to the song by playing different parts of the song: the intro, the first chorus, the last one, etc – and bypassing/ enabling the compressor plug-in so that you can hear the effect it has on the track. What you should be aiming for is making the song just a little more even without ruining its dynamics.
When you start hearing what the compressor does clearly (because trust me, this requires some finesse listening), try adjusting the attack and release times. Lower attack times make the transients in the song more emphasized while longer release times will flatten out the transients and dynamic spikes. Play with these until you find the right balance for your track. Next adjust the knee and the ratio and decide just how much gain reduction you want.
This part is where you make your song louder! Well, again, do not get too excited because you should not use this tool very dramatically either. The Maxim limiter in Pro Tools lets you set a ceiling amplitude for your song and then using the threshold parameter you can select an amplitude level for limiting.
The limiting process makes all peaks above the threshold come down to threshold level and at the same time it brings up everything below the threshold closer to the threshold level. Set the fader at unity gain (0) for your reference track and then see what the peak amplitude is on the master fader when playing it back. Try to set that value (usually something between -1 dB to -0.1 dB) as your ceiling. Drag the threshold down to -6 dB and see how that sounds.
If you want more you just have to lower the threshold. Again, listen carefully and keep going back and forth between your track and the reference track. Be careful to get even levels across all your tracks. Switch the Master Fader mix display to RMS and play through all the songs you are working on and make sure that you have got very similar RMS amplitude values. Remember to keep switching between RMS and peak digital VU so you also see when your songs peak and how much limiting is actually being applied.
Dithering and Bouncing
So you listened carefully, did some editing and did all the signal processing needed and you decided you finished. What next? Is your session in 24 bits and you will also export the song to 24 bits .WAV for digital distribution? If yes then you’re done and all you have to do is select each track (while “link timeline and edit selection button” is enabled) and then bouncing the track. (command+option-B / CTRL-ALT-B to open the bounce menu) Select your format and be careful to select Interleaved form the bounce menu, otherwise you will end up with two mono files.
If you want to bounce to 16 bits for CD you will need to add Dither. Dither is a random signal that is added to minimize the distortion added by the 24 to 16 bit conversion. To add Dither click on insert slot A on the master fader and select POW-r Dither. Select 16 bit and listen with both noise shaping types and see if you can hear any differences (I bet you won’t be hearing any difference). That’s it. You can go now through the whole bouncing procedure we looked at above.
The native Pro Tools plug-ins are not designed for professional mastering and you cannot expect your masters using the technique described above to get close to professional levels. The mastering chain might differ and it is possible to find better configurations than the one I exemplified which is a basic setup for learning to master. Nevertheless, with enough time and practice you can get amazing results from the all so basic tools provided with Pro Tools.