Many artists who are looking to hire a professional audio engineer for the first time may wonder why they need both mixing and mastering. I’ll elaborate in more detail below but let’s start this off with the key differences between the two processes.

Mixing is the craft of taking each individual recorded instrument (or audio track) and combining it in a pleasing way into one cohesive song. This includes blending instruments appropriately, balancing panning and depth, applying creative effects and generally giving the song it’s style, emotional tone and overall feel.

Mastering is the process of taking a final, stereo mix and finalizing it to fit into an album, an artist’s previous catalog and the wider music genre it’s a part of. This includes adjusting the dynamics of different frequency ranges (multi-band compression), adjusting tonal balance (EQ, harmonics), adjusting the sound stage (width), and finally adjusting the song to proper loudness levels (liming). A mastering engineer is also trying to make the song sound even better than the final mix, if possible.

With that quick description in mind, let’s dive into more detail about each approach to engineering a song.

What is mixing?

Mixing begins after a song has been written, produced, arranged, and recorded. These steps can be done in a professional studio by multiple musicians, engineers and producers, by one person, or anything in between.

These days producing is often done by the artist themselves. But producers are an important source of perspective and musical ideas. Do producers mix? Sometimes. Most of the time mixing is very minimal or broad during the production phase. Some producers are also mix engineers and will take over during the mixing phase once production is finished.

When I mix songs for my clients I receive a set of stems (or separate audio tracks) containing all instruments separated into individual high quality files. Most of the time editing and arranging will be finished so my job is just to work on dynamics, tone, texture, panning, depth and other effects to create an interesting and emotionally engaging piece of work. Let’s look into some of these steps.

Reducing conflicts: Using EQ and compression, a mix engineer will aim to give each sound it’s own space or at least reduce overlap that isn’t pleasing to the ear. This can be done by reducing dynamics/compression, increasing dynamics/expanding (like adding extra punch to a kick drum at a specific frequency), and most commonly by EQ’ing (or equalizing) a sound to fit in the mix and properly play it’s role in the song.

A song that is well-written and properly arranged, recorded and produced will take into account these conflicting areas during the production phase. This makes a mix engineers job much easier because we’re working with sounds that already “get along” well with each other.

Making sounds more appealing: After fixing any problems, an engineer will want to create the ideal sound for each instrument or instrument group. The goal is to make things sound even better than the recordings that were given to them. This can be challenging and sometimes unnecessary if you’re already working with high quality recordings. But some songs need a lot of work.

We will use creative effects and techniques to get each individual part of the song sounding as good as it can. This takes years of experience working with all types of instruments and songs. Certain engineers have techniques that are specific to their main genre which is why it’s good to pick the right mix engineer for your style of music.

The spatial touch: panning (left to right) and depth (front to back) are two very important aspects that give a mix a three dimensional quality. This is one area that really defines the difference in a high production value and a low production value song.

Panning is a great way to create width and the illusion of space. Double-panning is another great technique to widen an instrument or vocal so it seems to be coming from both speakers individually. Panning is very important and helps reduce overlapping sounds but too much panning can leave a song without enough body or “glue.”

Depth, or front to back placement is an illusion that can be created with reverbs and delays. A really good studio recording might already have a natural room sound built in. This subtle reverb gives the song a high production value from the beginning by creating a shared space that many of the instruments might have in common.

It’s good to experiment with using natural space when recording. This can be achieved by moving a microphone further away from a recording source so more of the room is picked up. It can also be achieved by setting up multiple mics as room mics and have them placed in ideal spots around a recording space.

During the mix process I will add depth when needed by using subtle room reverbs, long reverbs, synthetic (fake-sounding digital) reverbs, delays (echos) and any combination of these. These effects make an instrument seem like it’s coming from behind the rest of the song. It’s a good way to separate instruments that are less rhythmic or less important from the lead instruments. Anything can benefit from a bit of reverb but some things are better left totally dry.

Mixing can also be: tuning and layering of samples. Tuning is something I do when asked by a client or if I notice a vocal performance is a little rough.

Layering drum samples is another optional approach that helps punch up weak drum recordings. This is done by triggering a new drum sample at the same time as a specific drum hit that needs support.

The end goal of all this is to create a song that matches the vision of the artist and has the maximum intended emotional impact. This can be achieved in many different ways. A song is finished being mixed when the artist is happy, and hopefully impressed, by the final product.

What is mastering?

When the artist decides that a mix is final, and all the edits and revisions have been taken care of, it’s time to move on to mastering. Mastering is usually done with a batch of songs that are going to be released as one album. But quite often I’ll master singles to be released on their own.

Mastering isn’t just making a song louder. This is definitely a misconception. It’s also not as easy as people make it out to be. It takes a very experienced ear to do it well since it is an extremely subtle form of audio engineering.

The purpose of mastering is to focus on consistency and overall presentation in the wider genre the music is part of. Taking into consideration the artist’s historical style is also very important if they’re looking to have consistency throughout multiple releases.

Mastering is also a very important step if an artist is looking for a fresh perspective and a new set of experienced ears on their recordings. Mastering engineers place a lot of importance on their room, their speakers and their ability to detect extremely subtle details. Often times they will have much more detailed gear and multiple speakers styles to give their work greater context.

During the mastering phase, the engineer will receive each song as a high-quality stereo audio file. Sometimes a mastering engineer will receive reels of tape if that’s the chosen medium they mixed to. There’s also something called stem mastering that I’ve written about. Either way, the main goal is to make these songs sound even better than they already do.

EQ: Mastering engineers use EQ across the whole song. They don’t have access to the individual instruments (stems) at this point. They are focusing on an overall color and style. I also use EQ quite regularly to clean up any harmonic conflicts that were missed during the mixing phase. When I master songs I ask myself questions like:

Does the song have too much sub or bass?

Does the song have too much mud or mid-range build-up?

Does the song need more sparkle or air?

Does the song have any abrasive frequencies that will fatigue the listener?

I also listen for subtle issues that might sound bad on different styles of speakers or in different contexts. Learning to listen for these issues is one of the key skills of a great mastering engineer.

Dynamics: Sometimes a song will be too dynamic in a certain frequency range. Mastering engineers use multi-band compressors to focus compression on specific areas of a song. If a song is mixed really well, extra compression may not be necessary and could end up harming the natural dynamics of the song. De-essing is a form of narrow compression that reduces vocal harshness in the sibilant treble range.

Adding dynamics is also an option. When used sparingly, a subtle transient designer can help add some needed punch in certain areas. This is most often done during mixing but can be used in mastering when needed. Expanders are a similar tool to transient designers and act as a reverse compressor. Boosting sounds above a specified threshold.

Harmonics: This is another word for subtle distortion. It’s something that may or may not be used by a mastering engineer. I use it when I feel like a song needs a little more colorful excitement. If a song comes across as dull, a mastering engineer might reach for some sort of harmonic distortion effect to create a little sizzle.

Tape or tape emulation can also be used to warm up the sound or change the overall texture. This is usually done in the mixing phase but can definitely be used in mastering.

Width: Similar to mix engineers, mastering engineers also create width. This is usually done with a stereo imager. This tool let’s a user affect the width of different frequency bands. If a song seems like it’s not taking full advantage of the stereo field, this tool provides a solution. Too much width can leave a song without a strong body in the center area.

Loudness: The final phase is limiting. Limiting is just an intense form of compression. It creates a “ceiling” which is sort of a wall that stops louder sounds from clipping the audio system. It’s a very important step. The limiter will increase the overall loudness of the song by raising it’s level and compressing, or pulling down the peaks that are past the chosen ceiling. This creates a louder track that is also safe from clipping the various speaker systems it will be played on.

Final steps and flow: It’s also very important to make sure the songs match each other in tone and loudness and flow together seamlessly on the album. This keeps the listener engaged in one cohesive piece of work.

The final step is to prepare the songs for their final release medium. CDs, vinyl records, and digital releases are some examples. Most releases are strictly digital these days with vinyl making up a growing portion of music sales. CDs are still being manufactured and even cassettes have made a bit of a nostalgic comeback.

Each medium has a slightly different set of needs. The mastering engineer will make different versions when needed. Vinyl is usually mastered slightly different when it comes to loudness, treble, bass, and width. Cassettes can also have a slightly different mastering approach. CDs and digital streaming releases are usually pretty similar in style. CDs used to be mastered quite loud. Fortunately we’ve begun to relax this competitive loudness since most streaming platforms have a normalization algorithm to keep songs near the same volume.

Which is more important, mixing or mastering?

If you’re looking to achieve the highest quality sound possible, they’re both very important. But the easy, quick answer is that mixing is probably the most important. Mixing is where the song’s style and form is built. Mastering is very important but without a good mix you’re missing out on a very important step. Mastering can really help a bad mix sound listenable but it certainly can’t fix it in the same way mixing it could.

I hope this information helped you gain some perspective on what mixing and mastering engineers do. If you ever need an experienced audio engineer please feel free to contact me. Take a listen to my previous work and reviews from satisfied clients. I have affordable rates for independent artists and provide a very high standard of quality. I’d love to hear from you!