What Is Mastering: Definition, Process & Essential Tools

Understand the final stage of music production and how taking the right steps can make the difference in the pursuit of professional, release-ready results.

Depending on your experience and role within the music production world, there's a chance that your work is done when you export your project's multitrack, stems, or stereo mix. But in order to prepare your productions for the public ear, you'll need to apply sound mastering to your mix, too.

Audio mastering is often seen as a unique skill rather than an extension of a producer or mixing engineer’s regular role, but the task of a mastering engineer is often not understood. In this article, we’ve set out to define music mastering, dispel the myths surrounding the practice, and explain the importance of mastering in music today.

What is Mastering?

Mastering is the stage at which a near-final piece of music is processed in order to bring it up to final standards. These standards may be commercial, for example ensuring that the track is as loud as its contemporaries in similar styles; and they may be technical, for example ensuring that the format meets technical requirements for streaming services or other destinations.

First of all, let’s set the record straight on what audio mastering is all about.

Achieving the correct loudness

There’s a common misconception that sound mastering is mostly about turning up a mix to the desired volume without causing distortion. It’s true that loudness is one component of a mastering engineer’s role, but it isn’t the only one.

In the digital age, there are seemingly more and more loudness standards springing up which can convolute the entire process. Streaming platforms, film and TV, podcasts, CDs and vinyl records all demand a different dynamic range profile. It's down to the mastering engineer or music mastering service to understand these various standards and provide the relevant versions of the final track. Check out these six tips on loudness and dynamics if this is a part of the topic that gets your juices flowing.

Applying tonal and stereo enhancements

As well as adjusting a record’s loudness, a mastering engineer might make changes to a track’s overall tone using EQ and saturation, or make stereo enhancements such as widening the top end of a mix.

At the mastering stage, any changes should be extremely subtle, and should only serve to emphasize the existing qualities of a mix or to improve mix translation. One example of the latter would be to ensure that the low end of a mix is in mono, to ensure that it is mono-compatible. These 7 Tips for Mono Compatibility will help you to get there yourself at both mixing and mastering stages.

The last line of defense against audio issues

One huge reason for enlisting a third party or music mastering service to get your music over the line instead of doing it yourself, is that a second pair of ears may be more easily able to identify potential issues in your mix. If you’ve spent hours making and mixing a record, you might be deaf to a glaringly obvious pop, click or resonance. Or perhaps your emotional attachment to the music could get in the way of making objective mastering decisions.

For these reasons, it might be prudent to enlist a dedicated mastering engineer to carry out the final checks and apply the finishing touches to your project. This isn’t to say that serious issues can be fixed in mastering – these should be rectified at the recording or mixing stage instead. Unless the issue is relatively minor, the mastering engineer’s role here is only to identify and point out major problems so you can go back and fix it.

All that being said, time and budget constraints don't always allow for paying a mastering engineer. An AI music mastering service such as Waves Online Mastering is a quick and flexible way to achieve professional and polished productions, and you can try now completely free.

Why Do We Master Music?

Now we’ve looked at what audio mastering actually involves, let’s explore why mastering music is so important.

To avoid loudness penalties

As mentioned in the last section, each playback format and streaming service requires a slightly different level of loudness. This is to ensure that all audio plays back at a consistent-sounding average level so that the listener doesn’t have to frequently adjust the volume on their device.

If a streaming service like Apple Music receives a master that is too loud for their standards, they will simply turn it down. While this doesn't affect your music's dynamic range in itself, you might have applied a lot of compression and limiting to get your track to a particular volume. If your track then gets turned down at playback, then you've sacrificed your valuable dynamics for no additional level. A mastering engineer or online mastering service can make these considerations for you.

If you want to understand more about loudness for streaming services, check out this video on how to use the WLM Loudness Meter to get your masters right every time.

To ensure tracks hold up against other similar productions

Have you ever heard a radio or club DJ mix one track into another and it falls completely flat, sucking the energy out of the performance? When a quiet track is mixed out of a loud track, the natural human response is that we think the quiet track doesn’t sound as good. Of course a good DJ will identify that a quiet track will do this, but then they’ll be less likely to play it.

Either way, this highlights the importance of ensuring your tracks can stand next to other similar tracks within the same genre and style, which is a job for the mastering engineer. A great way to do this is by frequently referencing your tracks as you produce and mix, and by sending relevant reference tracks to your mastering engineer. Take a look at this article on The Science of Mix Referencing if you want to dig deeper into the subject.

Alternatively, you can use an online AI mastering tool such as Waves Online Mastering, which has been developed to ensure that your productions match that of other similar tracks, meaning they have the right impact wherever they are heard.

To make tracks, EPs and albums more cohesive to listeners

Aside from making sure your tracks are of a similar level to productions from other artists and labels, a mastering engineer will also ensure that each track on a release works together in a cohesive manner. From the general balance and tone to the loudness, listening to an EP or album of tracks with a variety of volumes and sonic qualities can make the project sound disjointed and unpleasant.

How To Master Music

While we’ve made it clear that there isn’t a ‘magic mastering chain’ that works for every record, mastering isn’t a guessing game, and there are some relatively standardized processes that can be followed.

Mastering has specific objectives, which are met using a deliberate workflow and specialized tools. Rather than blindly applying plugins in a cookie-cutter format, mastering is a reflective process of listening, diagnosing, processing, and reviewing - to bridge the gap between the mixdown and commercial release.

The following are the general objectives of mastering, and how to achieve them.

For a fast and effective route to a mastered song, try out the Waves Online Mastering Service.

Analysis and Diagnosis of Tonal Balance

Before getting to the creative and artistic elements of mastering, the engineer first needs to diagnose and fix any issues relating to EQ/tonal balance.

First, the track(s) will be listened to from start to finish, with the engineer making notes about any consistent or timed issues in the production and mix. They’ll ask themselves questions like “Is the track too muddy? Is it too harsh?” which give indications of areas to address.

These 10 Tips for Effective EQ during Mastering are a good place to start.

Solution: The tonality of a record is corrected and enhanced through the effective use of equalization.

Typically, engineers will start with subtractive EQ to remove resonant and fatiguing frequencies. Dynamic EQs like the F6 Floating-Band Dynamic EQ are perfect for this. Rather than being applied statically (all the time), they only activate when targeted frequency problems occur - preventing unnecessary frequency cutting or the need for automation.

After issues are fixed, engineers can start using additive EQ for more creative enhancements. Colorful, vintage-style EQs like the PuigTec EQ Collection are favorites here, and they can be used to add more character in the lows, mids, and highs.

Dynamic Consistency

Unmastered mixes can often sound like a collection of separate sounds and instruments, rather than one cohesive experience. A goal of mastering is to make tracks sound consistent and coherent, which requires careful usage of saturation and compression.

Solution: Create a more consistent listening experience with compression, so the listener doesn’t need to reach for their volume control. Make sure that there isn’t too much volume differentiation between sections.

Check out our guide on Limiting Tips for Mastering to learn how to get competitive loudness without crushing your dynamics.

What Mastering Can’t Fix

While mastering can enhance and polish a track, it’s not the right place to fix certain issues. It’s important to understand what mastering can fix, and when you need to send a track back to the mixdown stage.

Mix Balance Issues:

Mastering works on the summed file - meaning there isn’t much you can do to rebalance individual sounds and instruments. For example, you can’t turn up vocals without also turning up the snare or guitars occupying the same frequency range.

In fact, often these imbalance issues can be exaggerated by mastering processors like limiters, saturators, and compressors. Mastering is for enhancing (not fixing) mixes.

Unbalanced Low End:

While you can use multiband compressors to get some control and taming over low frequencies, this is an area that really needs to be addressed in the mix phase.

When balancing kicks and basses, you need to use sidechain compression and careful EQ carving on the mix channels.

You can add some extra color and pump up the master, but you can’t fix a disaster.

Bad Arrangement and Production:

If the fundamental composition and arrangement aren’t great, mastering a track won’t make much of a difference. If anything, it will highlight issues even more. The production quality and arrangement of the song itself can’t really be changed here. The rhythm, pitch, and timbre of the track need to work well before mastering.

Again, you can add some automation and additional polish, but if there are fundamental issues with the song itself, the mastering process won’t help.

Distortion and Noise:

Mastering involves compression and limiting, which raises the noise floor. If the mix contains clicks, pops, or clipped audio, mastering will only magnify these artifacts. You can achieve some correction with editing, but these are the kinds of issues that need to be fixed in the mix, not the master, to avoid further damaging the track.

Common Mastering Mistakes to Avoid

If possible, avoid mastering your own productions and mixes

As we've already highlighted, you should avoid mastering your own mixes. Instead, pay a mastering engineer to be the final set of ears on your project, or use an AI music mastering service such as Waves Online Mastering. This will ensure that the mastering process is distanced from the production and mixing stages, and will result in an objectively better master.

There is no magical mastering chain

A common question amongst those who are mastering their own music, or perhaps someone else’s music, is, “What is the best mastering chain?”. While there are a few common tools used in mastering, the truth is that there is no fixed chain that will sound good on every mix.

A good mastering engineer will listen to a track or a project as a whole, and decide what processes are needed to take a good mix and turn it into a great master. If the mix is already perfect, then the mastering engineer may decide to do nothing with it, in which case the value of the mastering engineer is in their second opinion.

The "Smiley Face" EQ

A common amateur mistake is blindly boosting the bass and treble to make the track sound exciting. This often hollows out the midrange, removing the body and presence of the song. Mastering EQ is a lot more nuanced than just cranking the highs and lows.

Over-Widening

There is such a thing as too much width! Using stereo expansion tools too aggressively can cause phase cancellation. This means when the track is played in mono (like on phone speakers or club systems), parts of the sound will disappear. Use phase checking tools, and always test a track in mono.

Ignoring the Meters

Mixing with your eyes is bad, but mastering without them is dangerous. Ignoring your metering plugins can lead to incorrect masters that get penalized and turned down by streaming platforms like Spotify and Apple Music. Check out this guide on Essential Mastering Level Tips to keep your meters in the right place.

Essential Mastering Plugins

Mastering Workflow Example

Every song requires a unique approach, but a typical signal chain and workflow focuses on color, control, and limiting.

Here is a modern workflow example:

1. Listen and Make Notes: Analyze the track with your ears (from start to finish), and take note of what you think needs to be processed.
2. Corrective EQ: First, you want to start by removing any frequency issues and excess. Use the F6 EQ to tame any harsh resonances. If it’s too damaged, consider sending it back to the mixing engineer for corrections.
3. Color & Saturation: Next add some analog characters. The BB Magma Tubes plugin is excellent for adding rich harmonic texture and warming up digital mixes before any compression happens. Alternatively, for a vintage vibe, the J37 Tape saturation adds a distinct glue.
4. Multiband Control: Now you want to start taming the dynamics. Use something like the C6 Compressor to lock in the low end, and control the balance and pump between frequency areas.
5. Final Limiting: Now you need to nail down the final output level. Place the L4 Ultramaximizer at the end of the chain. Adjust the threshold to achieve the desired loudness.
6. Export: Finalize the track and export to the correct loudness levels depending on the release platform - using the WLM Plus Loudness Meter. You may need to create a few variations depending on the rules of the distribution channel.

As above, every project will require a different approach when it comes to mastering and the tools required to get a track to its finished state, but we’ve identified some common mastering processes and some ideal tools for the job.

Corrective EQ - F6 Dynamic EQ

A mastering engineer might recognize a troublesome or resonant frequency that had been previously missed by a producer or mixing engineer. Using a versatile dynamic EQ such as F6 allows a mastering engineer to attenuate that frequency.

Additive EQ - Puigtech EQs

With the unwanted resonances removed, a mastering engineer might then turn their attention to more desirable frequencies and the overall balance of a mix. Using a characterful EQ such as the Puigtech EQs allows you to shape the tone of a mix in a colorful and musical way.

Stereo Enhancement - S1 Imager

If a mix is slightly lacking in the stereo width department or certain elements are positioned a little too wide, a mastering engineer might look to use a mid-side-capable stereo enhancer such as S1 Imager.

Compression - C6 Multiband Compressor

Much of the dynamic control of a track should have been completed at the mixing stage, but a mastering engineer may want to hit their limiter in a certain way. To accomplish this, they may use a multiband compressor such as C6, as this also allows them to focus on instruments or frequency ranges that are particularly dynamic.

Saturation - J37 Tape

Once upon a time, mastering was completed direct to tape, and many people with the warmth and tone that tape is known for. Using tape emulation plugins such as J37, a mastering engineer might choose to subtly impart some of the character of tape on a project.

Limiting - L2 Ultramaximizer

Often the final step in the mastering process, an engineer will use a transparent brickwall limiter such as L2 to bring up the overall volume of a composition to the desired level. A limiter will usually enable you to set a suitable ceiling and apply dithering too, but more on that here.

Frequently Asked Questions (FAQs) About Mastering

How Is Mastering Different From Mixing?

Mastering is the process that comes after the mix. Mixing involves balancing individual tracks (kick, snare, vocals) to make the song sound right, with all instruments coming across as intended and layered well. Mastering is the final polish applied to the rendered stereo mixdown, focusing on translation, consistency, and loudness.

Do All Songs Need to Be Mastered?

Yes. Mastering is an essential final quality control step. Even if a mix sounds great, mastering prepares the file formats, ensures volume consistency across an album, and guarantees the track sounds acceptable on all playback devices, while holding up against competition. An unmastered track won’t hold up.

Do I Need Separate Masters for Different Platforms?

It really depends on the distribution platform. Some streaming services have different level requirements. If you’re releasing on physical media like vinyl and CD, they’ll need slight variations too.

How Long Should Mastering Take?

For a single track, a master can take anywhere from 30 minutes to an hour or more. This can take longer if a track has a lot of issues that need fixing.

Conclusion

Mastering is an essential final stage of production that smooths the bridge between the studio and the listener. Thanks to modern tools, this once ‘dark art’ has now become much easier to understand and achieve from home studios.

With the evolution of tools like the L4 Ultramaximizer and the diversity of Waves Ultimate, achieving a release-ready sound is now within reach for every producer.

Originally published on February 4, 2024