What is music mastering?
Music mastering is the final step in the recording process. During mastering, additional audio treatments are applied to your mix to correct problem frequencies and enhance the musicality of your track.
Since magnetic tape replaced straight-to-lathe cutting in the late 1940s, audio mastering has become its own artform. But many in the music industry still see it as dark magic. Before we pull back the veil on this mystery, let’s define an important term.
An “audio master” is the final version of a song that’s prepared for sale, download, streaming, radio play, or any other form of mass consumption by listeners.
The audio master is what is used to make all future copies of the recording. It’s what is pressed on vinyl or burned to CD, and what digital services like Apple Music and Spotify use to encode the files of your music they make available. When you listen to a song via streaming, download or physical format, you’re listening to a copy of the master audio.
But how do we get that audio master?
Here are the steps an audio recording takes from beginning to end:
- A band or artist goes to a studio to record their music; for simplicity’s sake, we’ll say they’re recording one song. If they can afford it, they hire a producer or recording engineer who sits with them through the recording process to help them achieve a desired sound, or they just produce the song themselves. The artist and/or producer decide which takes during the recording are the best and compile each of those tracks.
- The artist or producer then sends those tracks to a mixing engineer. The engineer combines each instrument and vocal take into one song. This is called the mix. During the mixing stage, the engineer raises or lowers the levels of each track so they have their own place in the mix. For example: during the chorus the vocals take the lead, so the volume of the vocal track(s) is raised over the instruments to make the chorus stronger. Or maybe the bass guitar is too high, so the volume for the bass guitar track is adjusted to sit lower in the mix (or mixed out entirely if you’re Metallica on …And Justice for All). The engineer communicates with the artist as they work on the mix to make sure they approve how it sounds.
- Once the mix is finalized, it’s time for the last step: the mastering. The mix is handed to a mastering engineer (or some mixing engineers double as mastering engineers) to put on the final touches. The song is 99% done by this point. The mastering engineer’s job is to listen to the final mix and adjust the overall volume of the song and, if necessary, add any post-production effects or additional compression. In the audio world, this is called “sweetening” the song. It gets the song ready for commercial release and makes it more appealing to listeners.
Why should I master my music?
So, if your music is 99% done by the time the mix is finalized, why master it at all? Why not just release it as it is? The simple answer is that all serious artists include mastering as part of their music release plan. Why was it such a risky move for Kendrick Lamar to release his demo compilation Untitled Unmastered in 2016? Because artists rarely officially release music without it going through the mastering process.
Mastering puts a final sheen on the recording you worked so hard to create and the mix you went over with the engineer. It brings the sound of your recording to the same level as all the other millions of songs available (which is really important when one of your tracks is placed on a playlist; you don’t want it to suddenly be softer or muddier than all the rest).
Not mastering your music before release is like working tireless hours designing and manufacturing a beautiful car and then putting it in the showroom without a paint job.
How do I master my music?
Traditionally, artists hire a mastering engineer for this final step. As we outlined above, a mastering engineer takes the final mixes for the songs the artist has approved and works their magic. Finding a mastering engineer can be as easy as asking the engineer who mixed your music. They might have some favorite mastering engineers to recommend. The mixing engineer might even be a mastering engineer (though lots of mixing engineers don’t like to master their own mixes). If neither of those pan out, there are many mastering studios available. Do a search online and compare rates, and make sure to listen to some of what those engineers have worked on before to make sure you like their work. You can also check the liner notes or online credits of albums you enjoy to see who mastered that music.
In recent years, technology has made it easier for indie artists to mix and master their own recordings. Audio software called digital audio workstations (DAWs) like Pro Tools and Audacity provide tools for artists to record, mix and master their music right in their own home. Why don’t all artists do this? Because it takes a lot of work just to learn how to perform all these tasks, and even more work to complete all the steps yourself. Producers, mixers and mastering engineers still find work because their field is specialized. Most artists just want to make their music and let someone else worry about the tech wizardry that goes on behind the boards.
How much does a mastering engineer cost?
This varies from engineer to engineer and is dependent on a few things, like what you need done to the recording, how many songs you’re mastering and the length of the songs. If it’s just a “touch up” like making minor tweaks, it could be from $50 to $100 per song. For full services like adjusting EQ, volume and additional post-production effects, the average cost is about $150 per song. Many mastering engineers charge more for songs over 10 minutes, so if you’re a prog band prone to multi-part suites, be ready to pay more to master that epic half hour track.
This all might sound expensive, but keep in mind you’re not just paying for the engineer’s expert ears. Mastering studios have state of the art audio equipment and are built to be an optimal environment in which to listen to music, so the engineer is hearing your mix on the best equipment possible. This environment enables them to make accurate adjustments that you might not have been able to hear if you were to try to master on a DAW on your laptop.
Will my music sound better if I master it?
Mastering will make your final mix sound better, but only if the mix is already good, and only if the mastering engineer is judicious during the mastering process. The golden rule of audio mastering is: mastering won’t save a bad mix, but it sure can ruin a good one.
The last 20 years of music history have proved this to be the case. Renowned producer Rick Rubin has been at the center of at least two high profile cases of a poor mix being unsalvageable by the mastering engineer. His mixes for Red Hot Chili Peppers’ Californication in 1999 and Metallica’s Death Magnetic in 2008 were already far too compressed when they were sent for mastering, with engineer Ted Jensen explicitly stating the mixes for Metallica’s album were “already brick-walled before they arrived.” (“Brick-walled” is an audio engineering term for a mix or master that is too loud.) Similarly, Rush’s 2002 album Vapor Trails received backlash from both fans and critics for its overly compressed, distorted master. In Rush’s case, it’s not clear if a decent mix was ruined in mastering or if the mix was already too compressed, but the band didn’t take any chances and asked engineer Dave Bottrill to remix the entire album from the original instrumental tracks in 2013.
What is compression?
Audio compression or dynamic range compression is the practice of decreasing a recording’s dynamic range. In audio, dynamic range refers to the ratio of the loudest possible part of a recording to the quietest. The higher the dynamic range (DR) of a recording, the more drastic a difference there will be between the loudest and quietest parts.
You may have heard the term “Loudness War” used in a negative context in reference to a recording’s sound. This refers to the trend of mastering engineers (and even mixing engineers) applying increasing amounts of dynamic range compression to a recording so their song is louder than a song by a competing engineer working with another artist. In the ‘90s, labels and artists began to feel that their songs must be louder than others’ to attract listeners, and they began asking mastering engineers to make the recordings louder. Competing labels then asked their engineers to make their songs even louder, and so it continued, back and forth for over 20 years. This has resulted in audio that’s compressed so much that even the quiet parts are loud, and the louder parts are louder still. All dynamics in the recording are lost. Worse yet, over-compression can result in a phenomenon in signal processing called “clipping,” where the top of the waveform reaches past the peak, and becomes “clipped” because there’s nowhere else for it to go. Clipping results in loud, noisy and even distorted audio; not an optimal experience for the listener.
Why is the “Loudness War” bad for music?
Let’s put it this way: if even the quiet parts of a recording are loud, then we begin to lose a reference for what loud actually is. While a louder recording might sound better upon first listen when it “jumps” out of the speakers, many experienced audio engineers contend that “listener fatigue” is real. Listeners tend to return to a recording less if it’s too loud, and they might not even know why. Subconsciously our brains know dynamics, and recordings with a higher dynamic range have more staying power and replayability. In his New York Times op-ed earlier this year reflecting on the 2019 Grammy nominees, author Greg Milner says, “Loudness has its place, but most of us like our music to have breathing room, so that our eardrums are constantly tickled by little sonic explosions.” (For a truly nerdy deep dive in to the history of recorded music, I highly recommend Milner’s comprehensive book Perfecting Sound Forever.)
While louder songs have been successful in the short term, history is on the side of dynamic recordings. The Eagles’ compilation album Their Greatest Hits (1971-1975) is still the best-selling album in U.S. music history, and its recording and mastering is highly dynamic (“crankable” in audiophile slang). Bieber and Khaled might be appealing on first blush, but their recordings are so loud that after so many plays your brain tells you to turn them down, or hit “Next.”
Should I do different mastering for vinyl, CD or digital?
If you’re releasing an album and are planning on doing a vinyl edition as well as CD or digital, a different master is required for the vinyl version. This is because there are differences between what vinyl and CDs allow with regards to bit-depth, compression and the sequencing of the files. A master for CD must be 16-bit. It can also be as compressed as the artist would like, as CDs allow more space for the loudness that results from compression.
Since manufacturing vinyl involves physically cutting an analog of the audio frequencies into the surface of the record, there’s a limit to what can fit. Vinyl cannot accommodate clipped audio, so heavily compressed files will need to be adjusted to press to vinyl. The best source file specification for vinyl is 24-bit and dynamic. So if you decide to sell vinyl, that’s another reason to make sure your mix is not overly compressed before mastering! Vinyl also differs in its track sequencing, since there are two sides to a record instead of one for a CD. Vinyl masters are usually sent as two WAV files, one for each side.
Digital is not limited by physical space. A digital file can be as compressed or dynamic as you like, and either 16- or 24-bit. Some artists even sell two digital versions of their songs on their site or other that host two types: a 16-bit standard version and a “high resolution” that’s 24-bit. Those larger 24-bit files meet the specifications to be labeled “high resolution.”
What does Apple Digital Masters mean?
Apple Digital Masters (formerly Mastered for iTunes) is a designation on the iTunes Store for albums that meet Apple’s specifications to be considered high resolution. The files for these albums were mastered at 24-bit in an Apple-approved studio. When listened to with quality audio equipment, songs mastered at 24-bit sound better than those mastered at 16-bit. This is because the “bit depth” is larger, meaning the file is pulling more information. More information results in more detail and clarity being delivered to the listener’s speakers or headphones.
How do I qualify for Apple Digital Masters?
Apple lists the requirements for studios to qualify for Apple Digital Masters on their site. Only approved mastering studios can submit files for Apple Digital Masters. If you decide to distribute music for this program you’ll need to hire a mastering engineer who is approved by Apple.
Closing thoughts
We hope this article pulled back the curtain on an area of the music industry that for decades has been shrouded in mystery. With at-home tools like digital audio workstations, technology has made it easier than ever for independent artists to not only record and master their music, but also understand what actually goes into each individual process along the way.