What is Mastering? Mixing vs. Mastering

Mastering is often thought of as a mysterious art form. This guide aims to tackle that mystery head on—to not just explain what mastering is, but to outline how one might go about achieving the primary goal of any good mastering engineer.

Mastering is often thought of as a mysterious art form. This guide aims to tackle that mystery head on—to not just explain what mastering is, but to outline how one might go about achieving the primary goal of any good mastering engineer. And what’s that primary goal? It’s simple: to prepare an audio recording for distribution while ensuring it sounds at least as good (if not better!) when it goes out than it did when it came in. So let’s get started!

It All Begins with the Mix

You’ve just finished mixing what you think is a pretty good recording. The playing is good, the recording is clean, and the mix is decent. You export a file or burn it to a CD and proudly pop it into your audio player. Yet when you hear it played next to a commercial track from your favorite artist, you think that somehow your recording is missing that sonic “X factor.” You can’t help but wonder, “What’s wrong with my recording?”

Diagnosing Common Problems

It sounds small, and isn’t “loud” enough. Turning it up or mixing down at a higher level doesn’t solve the problem. Yes, that makes it sound louder, but doesn’t add the required impact or clarity.

It sounds dull. Other recordings are warm and deep yet bright and open—all at the same time. You try boosting the EQ at high frequencies, but now your song just sounds harsh and noisy.

The instruments and vocals sound thin and lack the same sense of fullness that your favorite recordings have. You patch in a compressor and adjust some controls, and now the whole mix sounds squashed. The vocal might sound louder, but the cymbals have no dynamics. It’s fuller… and lifeless.

The bass doesn’t have punch. You boost it with some low-end EQ, but now it just sounds louder and muddier, not punchier.

You can hear all the instruments in your mix, and they all seem to have their own “place” in the stereo image, but the overall image sounds wrong. Other tracks have width and image that you just can’t seem to get from panning the individual tracks.

You had reverb on the individual tracks, but it just sounds like several instruments in several different spaces. Your other CDs have a sort of cohesive space that brings all the parts together. Not like rooms within a room, but a “spaciousness” that works across the entire mix.

What Do I Do Now?

Mastering is a process that can, and with practice often does, take recordings to the next level. It might be the process that can address the problems listed above. What mastering shouldn’t be expected to do is completely reinvent the sound of your recording. Mastering is not a substitute for good mixing, or good arranging for that matter! “Loud” records are a result of good writing/arranging/mixing and mastering. They are made to sound good and loud (if loud is what you are after) from the get-go, not just at the end. Once you have reached the final step of mixing with something that represents your best effort, something that you are proud of, then it’s time to dig in and see how much further mastering can get you toward the sound that you hear in your mind’s ear.

You won’t become Bob Ludwig overnight, but you can make dramatic improvements to the quality of your mastered recordings with a little work.

In the end there are no right answers, no wrong answers, and no hard and fast rules. However, there are some well-known principles of audio production and mastering that are worth thinking through as you experiment. (And for goodness sake, have fun!)

What is Mastering?

Although there are many definitions of what “mastering” is, for the purpose of this guide we refer to “mastering” as the process of taking a mix and preparing it for distribution. In general, this involves the following steps and goals.

The Sound of a Record

The goal of this step is to take a good mix (usually in the form of a stereo file) and put the final touches on it. This can involve adjusting levels and general “sweetening” of the mix. Think of it as the difference between a good-sounding mix and a professional-sounding master. This process can, when necessary, involve adding things such as broad equalization, compression, limiting, etc. This process is often actually referred to as “premastering” in the world of LP and CD replication, but we’re going to refer to it as mastering for simplicity.

Consistency Across an Album

Consideration also has to be made for how the individual tracks of an album work together when played one after another. Is there a consistent sound? Are the levels matched? Does the collection have a common “character,” or at least play back evenly so that the listener doesn’t have to adjust the volume?

This process is generally included in the previous step, with the additional evaluation of how individual tracks sound in sequence and in relation to each other. This doesn’t mean that you simply make one preset and use it on all your tracks so that they have a consistent sound. Instead, the goal is to reconcile the differences between tracks while maintaining (or even enhancing) the character of each of them, which will most likely mean different settings for different tracks.

Preparation for Distribution

The final step usually involves preparing the song or sequence of songs for download, manufacturing, and/or duplication/replication. This step varies depending on the intended delivery format. In the case of a CD, it can mean converting to 16 bit/44.1 kHz audio through resampling and/or dithering, and setting track indexes, track gaps, PQ codes, and other CD-specific markings. For web-centered distribution, you might need to adjust the levels to prepare for conversion to AAC, MP3, or hi-resolution files and include the required metadata.

Approaches to Mastering

There are three ways to approach mastering. Let’s give these methods personalities and call them Ms. FixIt, Mr. Make-It-Better, and Ms. Nuts-and-Bolts.

Ms. Fix-It

Ms. Fix-it is someone who can recognize a problem with a recording. Too much bass, too little treble, too much dynamic range…whatever the problem, this person will work to rebalance things so they work better. In fact, they will probably sound more like the engineer heard them in the mixing studio.

Mr. Make-It-Better

This is the hot shot who knows how to add that little extra pinch of spice, whether it be sparkle or fullness or depth. Mr. Make-It-Better can take a good mix to an even better place.

Ms. Nuts-and-Bolts

This is the nerd. There are no sexy tricks and she doesn’t wear a superhero cape, but Ms. Nuts-and-Bolts is the person who will be sure that everything is done and done right. Under her watchful eye, every master that goes out is without technical flaws, and she’ll use the least amount of processing to get the best possible result.

In truth, every mastering engineer has all three personalities within him/herself, and knows when to call on each during the process of mastering.

Mastering Basics

Mixing vs. Mastering

We caution you against doing mixing and mastering in one step—that is, trying to master while simultaneously mixing a multitrack project. When trying to achieve both at once, you’re tempted to try to mix, master, arrange, and maybe even re-record within the same session. The separation of recording/mixing and mastering is very important. When mastering, you primarily focus on the overall sound of the mix and improving that, instead of thinking “I wonder how that synth part would sound with a different patch?” If you focus too much of your work on a single instrument in a complex arrangement, you likely will miss the fact that even if you have improved the sound of that one instrument, everything else has been impacted negatively. Get the mix you want, mix down to a stereo file, and then master as a separate last step.

An essential part of learning to master is to practice by mastering the work of others. It gives you good practice to listen to a wide variety of balances, tones, and dynamic range. Every engineer and producer has their own take on these things. A mastering engineer’s job is to try and get the vision of the engineer and producer (and ultimately the artist) to speak as clearly as possible. Once you have some experience experimenting with what sort of changes work or don’t work, you can do a better job of stepping back and evaluating your own projects with a slightly more objective ear. However, even seasoned engineers prefer to have someone else master their work, as they value the fresh perspectives that outsiders bring.

Mastering Effects

When mastering, you’re typically working with a limited set of specific processors.

Compressors, limiters, and expanders are used to adjust the dynamics of a mix. For adjusting the dynamics of specific frequencies or instruments (such as controlling bass or de-essing vocals) a multiband dynamic processor might be required. A single-band compressor simply applies any changes to the entire range of frequencies in the mix. Equalizers are used to shape the tonal balance.

Equalizers are used to shape the tonal balance.

Stereo Imaging can adjust the perceived width and image of the sound field.

Harmonic Exciters can add an edge or “sparkle” to the mix.

Limiters/Maximizers can increase the overall level of the sound by limiting the peaks to prevent clipping.

Dither provides the ability to convert higher word-length recordings (e.g. 24 or 32 bit) to lower bit depths (e.g. 16 bit for CD) while maintaining dynamic range and minimizing quantization distortion.

With all these types of effects, you might wonder where to start. First off, remember, just because you have all these modules doesn’t require that you use them all. Only use as many as you need. In truth, there really isn’t any single “correct” order for effects when mastering, and you should feel free to experiment.

My preferred order usually is:

  1. Equalizer
  2. Dynamics
  3. Post Equalizer
  4. Harmonic Exciter
  5. Stereo Imaging
  6. Loudness Maximizer

If there is something that comes close to being an iron-clad rule, it is that when you’re using the Loudness Maximizer and Dither, they should be placed last in the chain.

General Recommendations While Mastering

While you should educate yourself about the function of individual tools in your toolbox, ultimately the tools themselves do not make the sound. They are designed to help the sound, so you’ll want to decide what sort of help the sound needs. This may sound obvious but just like a good cliché, the obvious truths are often obvious because they are so very true.

The fact is that nowadays we have digital signal processing (DSP) tools that are vastly powerful and allow you to change, twist, repair, and contort your sound a million different ways. It is also true that the more involved the processing, the greater the potential for harming the original sound. A multiband tool will do much more “damage” than a single-band tool. A Mid/Side process will create problems that a standard stereo processor will not. Be careful! Before deciding you need the latest whiz-bang feature, figure out what the goal is. Then you can decide which tool is best to use.

The Mastering Mindset

Your thought process might go something like:

  • Step 1: Listen: “Hmm, I think I have identified something I would like to change.”
  • Step 2: Assess: “What tool or technique would be best to make that change?”
  • Step 3: Experiment: “Let’s try it out.”
  • Step 4: Evaluate: “OK, I tried it…but did it work?”

Once you decide if your experiment worked, you can determine whether you need to go back to Step 1 or Step 2. Do so as many times as necessary to get to where you are satisfied.

Mastering Tips

  1. Have someone else master your mixes for you. In many project studios, the same person is often the performer, producer, mixer, and mastering engineer. If hiring a trusted mastering engineer isn’t an option, at least get someone else to listen with you. You could also find someone who will master your mixes if you master theirs. Why? Well, if you have the tendency to add too much bass or not enough top end due to your listening environment, those tendencies will be compounded in the mastering. It’s common for the mix engineer to be too close to their own music. You’ll focus on some things other listeners won’t hear, and you’ll miss things that everyone else does hear.
  2. Take breaks and listen to other CDs in between sessions. Refresh your ears in terms of what other stuff sounds like. Even seasoned pros, who instinctively know what sound they’re working towards, will take a moment to listen to a familiar recording and recalibrate themselves during a session.
  3. Listen on other speakers and systems. Burn a few different tracks to a CD or MP3 player and play them on your home stereo system, or drive around and listen to it in your car. Don’t obsess over the specific differences; just remind yourself what other systems sound like.
  4. Check how it sounds in mono. This can’t be stressed enough. A good ratio between mono (correlated) and stereo (uncorrelated) information is very important in many contexts; broadcast, LP/vinyl cutting, and even MP3 creation. When you listen in mono and important instruments vanish, or if the level drops significantly, you might need to rethink what you are doing.
  5. Monitor at around 85dB SPL (C-weighted). How loud is that? Turn up your speakers until you can still have a conversation with someone who is a meter away without having to strain your voice. That’s just about right. When you listen at low to medium volumes, you tend to hear more midrange (where the ear is most sensitive) and less of the lows and highs. This is related to something called the Fletcher-Munson effect, which involves how different frequencies are heard differently depending on the playback volume. So check from time to time how it sounds at different volume levels.
  6. When you think you’re done, go to bed, and listen again the next morning.

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