After you have finished recording and mixing the tracks in your music production, you probably know that the next stage in the process is mastering the audio. But what is audio mastering exactly?
Audio mastering can seem like it’s shrouded in secrecy, and that only a select few members of a secret society can do it. While it’s true that mastering can take a lot of expertise and some expensive equipment, it is something that you should try to understand and have a go at doing it yourself wherever possible.
What is Audio Mastering?
Mastering is a term that comes from the history or record production. The master disc was used for producing all the reproductions of a recording on disc, and these discs would be sold in record shops.
Vinyl records seem to be making a comeback so it won’t be so hard for young people to imagine this process as I thought it might be a few years back.
The process that we call mastering nowadays used to be called pre-mastering, and it was the process of getting the audio ready to be cut into the master disc.
During this modern mastering process we need to prepare our audio production so that it will sound as good as possible on as wide a range of audio equipment as possible.
It’s been said that the mastering process adds “polish” to the music production. This implies that the music would function and sound okay without audio mastering. However, the mastering process adds the final touches that will make your music stand out and sound consistent with other professionally produced recordings.
Mastering Your Productions Yourself
The accepted view on mastering music for “professional release” always seemed to be that you couldn’t do it yourself (or you’d be crazy to try) and that you absolutely had to send your production to a mastering studio (or mastering house) to have it done properly.
However, the meaning of “professional release” has changed over the last few years. Anyone can release their music on a website like Soundcloud, and it’s not that difficult to get your music on a streaming service like Spotify.
You want your productions to sound professional and be as good as, if not better than, other similar music. Professional mastering services can help you with this, and they really aren’t very expansive at all.
However, if you understand the audio mastering process and know how to do it yourself then that has to make you a better producer. It will help you to understand the recording and mixing process better too, since you will know where the process is headed.
This is true whether you decide to master your productions yourself or have them done by a mastering engineer in a mastering studio. So let’s have a basic look at what’s involved in doing your own audio mastering.
Simple DIY Audio Mastering
People sometimes think that what you send to the mastering studio is all the tracks from your production. This is almost never the case.
What you would normally send to the mastering a studio is a stereo audio file. This is the end result of your careful recording and mixing process, and the mastering engineer uses this as the starting point for the mastering process.
Only having access to a stereo audio file places limitations on what the mastering engineer can do, since they can’t go back to individual tracks in the mix to make alterations.
This is why it’s always emphasized that you need to mix your production properly since the mastering engineer can’t go back and fix mixing problems since they don’t have access to the specific tracks, only the single stereo audio file.
If you are going to master your own music, then having access to the individual tracks as you go through the mastering process can be helpful. You should finish mixing your track before you move onto the mastering stage, but at least the ability to make adjustments to tracks within the mix can be helpful.
Something to bear in mind is the sample rate and bit depth of the audio files that you will be working with. Even though your final mastered track may be exported at 16-bit resolution and 44.1kHz sampling rate, it’s usually recommended that you work with higher resolution audio during the mixing and mastering process.
Storage space isn’t normally a problem with modern computers and storage devices, and you can manage the CPU load required by higher resolution audio so this is unlikely to be a limitation. Keeping the audio at as high a resolution as possible through the process is thought to help produce better results.
Prepare Your Stereo Audio File for Mastering
Once you are satisfied that all of the tracks are mixed the way you want them, including effects and automation, you should start to organize them ready for moving things forward.
To avoid tinkering with instrument and effects settings on tracks you can render each individual track in your piece as an audio file. Even if it was an audio file to start with, this will let you embed any effects and automation in the individual audio files.
It’s important to make this commitment to the final version of each track. You’re saying to yourself that you this particular track is done and you won’t be tweaking it any more.
Once you have these “multitracks”, some mono, some stereo, you can combine them into specific instrument or element groups to generate the “stems” that make up your piece of music.
You can adjust the levels of the individual tracks within each group to balance the mix for that group before rendering those tracks as a group audio track or stem. Now you will have a smaller number of audio files with names like “Drums Stem.wav”, “Keys Stem.wav”, “Vox Stem.wav”, and so on.
Rendering the original multitracks as stems enables you to reduce the overall number of tracks you are working with. It also provides another point at which you make a commitment to the sound of the files you have produced.
If you don’t make these commitment steps at each stage of the process it’s too easy to keep going back and forth to the original tracks, even instrument settings on midi tracks, if you don’t commit to the audio files.
You can now adjust the levels of the group stem audio files as you listen to them playing together before rendering them into a single stereo audio file.
Listen to Your Stereo Audio File
When people start off trying to master a track themselves they often jump straight into the process of using plugins and other devices to alter the sound. They want to use EQ, exciters, compressors, limiters, and anything else that might work magic on their music.
What they often forget to do is listen to their audio file.
One of the things that makes professional mastering engineers “special” is that they actually listen carefully to the sound coming out of the speakers (or headphones). People trying to master their own recordings often don’t spend enough time on this.
Remember, mastering is about making your music sound as good as possible, on as many different types of audio equipment as possible.
Listen to your audio file through the headphones that came with your phone, with the best mixing headphones that you have, your studio monitors, the speakers in your car, the bluetooth speaker you take to barbecues, and whatever speakers you normally listen to music on at home. If you have access to PA speakers or you can play it in a night club then do that too.
Each time you listen to the recording think about what you are hearing. You are trying to get an overall impression of what sounds good and what doesn’t sound so good. Also, listen carefully for any unwanted noise at this stage. Listening on all of these different speakers and in different settings gives you a good opportunity to pick this up.
Make a note of the type of noise and the time within the piece of music that it occurs. We’ll come back to this later.
Think about your emotional response to the music. When you finished recording it you were probably quite excited that you had “finished”. When you were mixing it you were probably enjoying the way your adjustments and use of effects was making it all sound better.
But what about now? How does it make you feel? According to mastering maestro Bob Katz, you need to be thinking about what you can do to make the music more exciting. Hopefully it is already be pretty exciting, great melody and harmony, maybe with a great vocal performance, and now you want to make it sound as good as possible.
Load the File in Your DAW and Listen in Your Studio
However, it is important to be aware of the ways in which your studio speakers and the way that sound reflects off the walls and other surfaces can affect the sound that you are hearing.
You should now load stereo audio file of your recording into your music production software or DAW (digital audio workstation). You should start a new project for mastering since you need to separate this activity from the recording and mixing process. This is why it was recommended that you commit to
1. Listen for Unwanted Noise
During the mixing process you should have picked up any unwanted noise and removed it. However, it’s possible that some unwanted noise sneaked through when the tracks and stems were rendered to audio.
It’s important that any unwanted noise is removed at this stage. A key part of the mastering process is increasing the loudness of the recording, and you don’t want the loudness of these noised increased too.
While you were listening to your music on different headphones and speakers, and in different settings, you should have made a note of any clicks, hums or other unwanted noise and when it occurs in the piece.
As you listen through your recording on your DAW you can zoom in on the points where the noises occur and mark where it occurs.
Removing noise from the stereo audio file representing the entire mix can be tricky, so this is where having your group stems and multitracks available can help.
Listen to each group stem and see if the noise is in any particular audio file. If it is, listen to each of the audio tracks that make up that group stem and see which one contains the noise.
In this way you can work to remove the noise from any affected audio tracks. You can then render the tracks into a group stem, before producing a new stereo audio file, which should have much less noise present than before.
Engineers in mastering studios don’t usually have access to your group stems (although they might have these) or individual tracks. They normally use software to remove noise, which can be expensive, so having access to the tracks when doing it yourself helps to avoid this expense.
2. Listen to a Reference Track in Your DAW
Import a song or track in the same style or genre as the piece you have produced to refer to as you master your recording.
If you have ever played a professionally produced and mastered track in your DAW you will probably have been struck by how different it sounds to the music you are producing. It can actually sound quite strange if you’re not used to listening to professionally mastered music in this way.
Listening to the reference track and comparing it with your production lets you hear what you are aiming for in terms of tonal balance, dynamic range and how exciting the track sounds. At this stage your production probably sounds quite flat in comparison.
3. Apply EQ (Equalization)
As before, the starting point for applying EQ is to listen to your track. We’ll refer to it as the track from now on since that’s what it is – one stereo audio track in your DAW.
As I mentioned earlier, many people try to mix and master their music visually rather than by listening to the sound. Visual tools are designed to help you, but are not meant to replace your ears.
Listen to the balance between the low and high frequencies, listen for the sounds of the individual instruments and voices within the mix. You will have been doing this as you mixed the individual parts in your recording, but you will need to revisit it during the mastering process. This will help you decide what needs to be adjusted using EQ.
To summarise, EQ controls let you choose particular frequencies and either boost or cut the level of the sound at that frequency. Some EQ plugins only let you do this at one frequency, most let you choose and adjust the levels several separate frequencies.
It’s often tempting to boost the level of a frequency to give it more impact. However, the recommendation from professionals is usually to cut the level of frequencies around the one you want to emphasize, as this helps it to stand out in a more pleasing way.
The types of thing that mastering engineers are listening for, using terms they would use, is whether it sounds muddy and lacks definition, sounds boomy, sounds thin, or is a bit “toppy”.
These are all problems that can be reduced or fixed using EQ. Here are some brief suggestions from Waves, a company that makes effects plugins, that you can try in relation to each.
Sounds Muddy and Lacks Definition
If your track sounds muddy and lacking in definition it is may be because the mid-range frequencies are dominating the overall sound. If you reduce the level of the sound in the 150-350Hz range it may help. This will help to emphasize the lower and higher frequencies, by cutting the level of the frequencies above and below respectively.
The Mix Sounds Thin
If the track sounds “thin” or lacking in substance, you may the opposite of the problem above. A thin sounding track often lacks energy in the mid-range, so you could try boosting the level around 500Hz to see if this helps.
The Track Sounds Boomy
A track that sounds “boomy” often has too much energy in the lower audible frequency range. You could try reducing the levels of frequencies around 100- 150Hz.
Try doing this by cutting the specific frequency range, leaving levels above and below unaffected, and by applying a cut to all frequencies below 150Hz and listen for which works best.
The Track Sounds Toppy
If the track has too much energy in the higher frequencies it is said to sound “toppy”. This isn’t the very high frequencies where things like cymbals live (see below), but the higher frequencies occupied by other instruments, around 3-8kHz. Reducing the level around these frequencies can restore the balance.
The Sound is Dull
A lack of very high frequencies can make your track sound dull. Boosting the level of frequencies above 10kHz can give your track a little extra “zing”. However, you have to be careful not to over-emphasize things like cymbals since high frequencies can really stand out.
The Track Lacks Presence
Lack of “presence” usually means that it seems like something is missing. The most noticeable part of a recording is usually the lead vocal or lead instrument (e.g. guitar or piano), and it’s usually this that doesn’t seem to stand out.
Lead vocals and instruments can be emphasized in the track by boosting levels around 3-5kHz. Take care not to boost the levels too much since making these elements stand out too much can make the track sound unnatural.
4. Make Adjustments to Dynamic Range
Once you are happy with the balance between the different frequencies in your track you can move on to make adjustments to the dynamic range. This is normally done using a compressor.
A compressor lets you reduce the volume of louder signals without affecting the quieter signals. With the volume of the louder sections reduced you can increase the overall volume level of your track. This has the effect of making the track sound louder, and as a result it usually sounds better too.
If you are still having problems with particular frequencies in your track you can use a multi-band compressor, which lets you target a number of specific frequencies at the same time.
For simplicity, we’ll assume that you have managed to balance the frequencies using EQ and are going to use a single-band compressor. The name suggests that a single-band compressor lets you target a particular frequency range, but here we are using the term to mean a compressor that doesn’t target a particular frequency. This means a compressor that, in theory anyway, compresses all the frequencies equally.
I have read all sorts of complicated information about using compressors, and I have found it quite difficult to follow some of it. Compression seems like it should be simple. 1. You reduce the volume of the sound that goes above a particular threshold level, which can make the track sound quieter. 2. You turn the volume back up using the make-up gain control, and hey-presto, the whole thing sounds louder.
My simplistic view of this was reinforced recently when I was trying out a free-compressor plugin. It had two main controls – compress and make-up gain. It’s called a Klanghelm MJUCjr – it’s free and I recommend that you check it out.
I had been trying to get a dance-type track to make me feel like dancing for months and nothing really worked. I liked the overall sound of the track but it just sounded tired and I couldn’t seem to fix it. I tried fancy mastering plugins, and none of them made the difference I was looking for.
So, back to my free compressor. I removed the other fancy plugins and I put it on the track with both controls and 12 o’clock. The difference was incredible – the track jumped out of the speakers and sounded happy and powerful for the first time.
So, maybe for DIY mastering purposes it’s helpful to keep the use of compression nice and simple like this.
5. Add Harmonic Enhancement and Stereo Widening
As producers try to find more ways to make their tracks sound better they might use a harmonic enhancer or exciter to give their productions more sparkle. Most of the information available on this, apart from that provided by the makers of these devices, advice caution.
They are described as being addictive, and they can have a very significant effect on the sound. Sometimes people try to use them instead of proper EQ and compression to make a track sound better. Rather than using them selectively on particular frequencies it’s easy to apply them to the whole mix and, this seems to end up clouding the producers judgement.
In the example of my dance track that I described above, I had been trying to use a harmonic exciter to give it what I thought was missing (although I didn’t really know what that was). I wasn’t using any judgement, just applying it and hoping for the best.
Stereo widening is sometimes used to give a section of a track, such as the chorus, a different kind of impact. During the mixing process you will have applied stereo effects where necessary and it may not be necessary to do anything further at this stage.
If not used carefully stereo widening at this stage can give the impression of a “hole” in the middle of the track where something seems to be missing. It’s probably better to apply stereo effects to the individual parts of the overall mix at an earlier stage.
6. Apply Master Limiting
The final stage of the mastering process is usually to add a limiter so that the overall level of the track can be increased without exceeding the threshold that leads to “clipping” and unpleasant digital distortion.
The level that must not be exceeded is 0dBFS (decibels full-scale). Decibels can be quite confusing, and there are a number of different scales using decibels.
Decibels Full-Scale starts at 0dB, which is the full-scale, or maximum, level that a digital system can handle without producing distortion (also called clipping). The final level output needs to be below 0dBFS for this reason.
Despite being compressed at an earlier stage in the process, the different sections of the track will still have different maximum, or peak, levels. For example, the verse may be quieter than the chorus, and there may be a breakdown section that is quieter than the verse.
You will need to listen to your track and watch the peak level as it plays. You can then adjust the limiter so that the level is still just below 0dBFS at its peak. It’s normally recommended that the peak level should not be higher than -0.3dBFS just to be on the safe side.
7. Exporting Your Master Track
While recording, mixing and mastering your track you will have been working in 24 or 32-bit resolution (hopefully). When you export your master track you will need to think about the format to use in terms of bit depth and sample rate.
If you are going to burn it to a CD (I guess people still do that?) you will need to use 16-bit resolution. Streaming services like Soundcloud also prefer 16-bit resolution.
When you are reducing the bit resolution of your track while exporting it you will need to apply dithering. This adds some low-level random noise that reduces the risk of artefacts being introduced by the loss of resolution during export.
Final Thoughts on DIY Audio Mastering
So mastering isn’t a mysterious process that can only be done by mastering engineers with super developed hearing, using hyper-expensive hardware and software. You can do it too.
Although professional mastering services aren’t that expensive on track-by-track basis, and you might not get such good results yourself, why not give it a go.? It’s another important skill that you will learn and it’s fun too.