What does mastering audio mean?
In music production, mastering is the final stage of the production process. It’s the last chance to make adjustments to your songs before they’re released to the world.
When you master music, you’re working with all of the songs that are going to appear on one release e.g. an album, EP, etc. Each of the songs has already been mixed, and you’re now going to make alterations to things like the overall level, frequency response, and dynamic range of each song. This is carried out to give the songs a sense of uniformity and balance. A process that ensures all of the songs sound as though they belong on the same release. Mastering is also carried out to ensure that your album sounds comparable to existing releases in the same genre.
Additionally, mastering is an opportunity to make tweaks to ensure that the songs sound their best on all of the target listening systems. This could be headphones, iPod ear pods, home hi-fi speakers, club PA, etc. Mastering is also usually the point at which fades are added at the beginning and ends of the tracks. Finally, mastering involves the creation of the final files in suitable formats.
Whilst mastering can involve numerous different processes to shape the way that your songs sound, many mastering engineers create fantastic masters using just EQ, compression, and limiting. In this lesson, you’ll discover how to master music in 4 easy steps.
Before we begin
Before we begin, there are a couple of things to consider before you start to master music. First of all, mastering can’t fix a bad mix. If you’re not happy with the mix, you would be better served going back to the mixing stage and creating a mix that you’re happy with before progressing to the mastering stage. Also, before bouncing your mixes for mastering, it’s good practice to ensure that there is at least 3dB of headroom between the loudest peak and 0dBFS.
Step 1 to master music: EQ
The first stage in this 4-step process to mastering your songs is to manage their frequency content. Naturally, there may be some variation in the frequency response of each of your tracks. Perhaps the instrumentation differs between songs. Perhaps different songs were recorded in different spaces or with different mics. Using EQ on each track allows you to ensure that all of the songs on your album sound similar tonally. Of course, some tonal variation may be desired. For example, you might want one song to have a darker vibe than the rest. But they should still sound as though they belong on the same album. EQ at the mastering stage lets you take control of the frequency response of your songs and present them in the way that you think sounds best.
A reference track is really useful here. Picking a track that you think sounds great, has similar instrumentation, and comes from the same genre, gives you something to use as a comparison for your own master. In General, you’re looking for a balanced frequency response. A reference track can reveal whether your song has too much high-frequency content, making it sound harsh, or too little, making it sound dull, for example. Now is your opportunity to balance the frequency spectrum of each song on your release to make them sound their best.
Be sure to level match your reference track with the songs that you’re mastering. If your reference track is louder than your own tracks, then it’s hard to make a fair analysis of the requirements of your songs without being influenced by the difference in level. Generally speaking, small EQ tweaks at this stage can make a big difference.
Step 2 to master music: Compression
Step 2 in this process to master music is to apply compression to control the dynamic range of your songs. Perhaps some songs sound a little too lively. Compression can rein in the dynamics and add some ‘glue’. Much like EQ, these changes should generally be subtle. Ratios of 2:1 are common in mastering. Gain reduction of just 1-2 dB will likely make a big difference. During the mastering process, a multiband compressor is often used. This splits the compressor up into multiple frequency bands, each with its own compression settings. This helps to focus the compression into the desired areas. Personally, however, I tend to keep things simple and use a single-band compressor.
Something to keep in mind when mastering is that you don’t necessarily have to apply compression. Only use it if you feel that the tracks would benefit from it. Also, keep in mind that you don’t necessarily have to manage the dynamics of the song using compression. If you feel that the verses in a song are too low in comparison to the choruses, then you may be better served by adjusting the gain of the song to bring the verses up or the choruses down using level automation, rather than trying to bring down the level of the choruses using compression.
Step 3 to master music: Limiting
The 3rd step in this mastering process is to manage the level of your songs. A key tool in setting the level of your songs is a limiter. That’s because limiters can be used not only to raise the overall level of your songs but also to ensure that your songs don’t peak higher than a certain point.
A limiter is a compressor with a really high ratio. Generally, a ratio of around 10:1 is considered to be limiting behaviour. But standard limiters cannot necessarily be relied on to catch every peak and hold the signal below a certain point. As such, a ‘brick-wall limiter‘ is used in mastering. A brick-wall limiter is a limiter with an extremely high ratio, typically infinity:1, and one which is able to ‘look ahead‘ to see peaks coming in order to ensure that the signal does not peak higher than a certain point. Most major DAWs ship with a stock brick-wall limiter.
Controlling a limiter
The way limiters are controlled varies between designs. Perhaps the most common is a design that provides ‘threshold and ‘ceiling’ parameters. The threshold parameter sets the level that the signal will be limited to. But crucially, the threshold parameter is also tied to the output gain. So as you dial down the threshold to increase the amount of limiting that is applied to the signal, you also raise the limiter’s output level. The limiter’s maximum output level is then controlled by the ceiling parameter.
An alternative design is one that provides you with ‘input gain’ and ‘output’ parameters. In this case, the threshold is usually determined by the output setting so that the signal is not allowed to peak higher than the limiter’s maximum output level. The input gain parameter is then used to control how much of the signal is limited, and by how much the gain is increased.
Other parameters on a limiter vary. Some offer control over the look ahead setting. Some offer control over the attack and release, some only the release, some don’t offer control over either.
How loud should my master be?
So, how much limiting should be applied? How much should we raise the level? Where should the output/ceiling be set? Well, in modern-day mastering, there are two measurements that you need to be aware of when setting your song’s levels. They are ‘loudness unit full scale’ (LUFS), and ‘decibel true peak’ (dBTP). Many modern DAWs, mastering plugins, limiters, etc. have LUFS and dBTP meters built-in, but if yours doesn’t, you can measure both LUFS and dBTP using the free YouLean loudness meter. I’ve written in-depth lessons on LUFS here and dBTP here. But in short, my advice is that you master the level of your songs to have a short-term LUFS value of no louder than -10 LUFS, and you set your ceiling/output so that your music peaks no louder than -1dBTP.
Step 4 to master music: Creating the final files
The final part of this 4 step process is creating your final files. If you haven’t done so already, this is a good time to add fades at the beginnings and ends of your songs. Then, with your fades in place, and satisfied that your songs sound their best and sound great on your target listening systems, it’s time to bounce your tracks.
Most digital distributors require a lossless file e.g. WAV, AIFF, etc, with a bit depth of 16 bits, and a sample rate of 44.1kHz. A 16 bit, 44.1kHz, lossless file is also the correct file type for audio CD and remains something of an ‘industry standard’ for the final files. Some digital distributors will allow you to submit a different file type if you wish. Personally, however, I would recommend sticking to this standard. Some platforms may insist that you send a different format file. If that’s the case then go ahead and bounce your final files in their required format.
When you bounce your 16-bit file, you’ll need to add dither. You can read the full breakdown on dither here. Additionally, if you’re having CDs manufactured, you could create a ‘DDP image’. A DDP image is the master file format for CD pressing. The DDP image will contain all of the data that the CD requires. This includes the songs themselves, the length of the gaps between the songs, and metadata such as the artist, song title, etc. Software like WaveLab and Hofa CD-Burn.DDP.Master can be used to create a DDP image. When uploading songs to a distributor for digital distribution, you will usually need to enter the song titles, artist’s name, and other metadata manually when submitting your music.
With this 4 step process to master music in your home studio, you can create fantastic-sounding masters using only EQ, compression, and limiting. This process ensures that you make your tracks sound great and that you handle things like dither correctly. It also helps you keep on top of modern loudness measurements like LUFS and dBTP. Plus it ensures that you create files in the correct format, ready for release. Try it out on your next mastering session.
What’s your process for mastering? Do you master using reference tracks? Do you check that your masters sound great on target listening systems? Leave your mastering questions and suggestions in the comment box below.
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