5 Audio Mastering Tips
The mastering engineer is the last step of the artistic phase, and the first step of the manufacturing phase. It’s the final opportunity to listen, polish, and make a change in the sonic presentation. It is also the first step of the manufacturing phase, because it prepares the master in the way that best suits the needs of the manufacturer.
The goal is to listen to the broad picture; the actual content is immaterial. The mastering engineer is paying attention to EQ presentation, to level presentation, to dynamics presentation. It’s taking a collection of songs, and creating a flowing body of work.
A Bit of History
Mastering has changed greatly since the late 1950s, when mass-produced music became the norm. At the time, record labels owned studios, and the labels employed the engineers. Engineers started their careers as apprentices, and the first stop on their path was to apprentice with the mastering engineer. This was to develop and hone their listening skills. The mastering engineer was responsible for transferring the final tapes from the mix/balance engineer, and ensuring that the transfer to lacquer (the master at the time) was as accurate as possible. The whole goal was to duplicate the tape sound on the disc. In the process of apprenticeship, the new engineer listened to hundreds and hundreds of transfers, and learned the subtleties of this art from a seasoned professional. As the new engineer gained skills, he or she typically moved to training with the mix engineer, and recording engineer.
As the studio/label relationship broke down over the years, engineers became independent, and started working in different studios. The challenge here was that each studio had a different mix environment. The engineers were then tasked to polish the results from a less familiar environment, using the tools they had at their disposal: EQ, dynamics, processing, and levels. This is the situation we are still in today, in which the role of the mastering engineer has expanded to become the final check for both the technical and artistic aspects of a project.
1. Be Prepared
When you show up at the session, it’s essential that you are prepared. You should clearly label which are the final mixes you’d like the engineer to use. You should have all the details of the file finalized such as song titles, sequencing, and metadata such as ISRC codes and CD text. It's also important to have documentation of any known problems with the files as well. Accurately note the existence and location of glitches, digital errors, distortion, bad edits, and level problems. This will save a lot of time and money during the mastering stage.
Additionally, you should know who the manufacturer will be, and what their requirements are for type of master and method of delivery. Make sure the songs have been accurately timed out, so that they will comfortably fit the size of the intended format(s). If you are supplying the pre-master mixes on an analog format (like tape), it is very important to include full reference tones and documentation of the specifics. This assures that the material will be played back at proper levels and bias.
2. Provide Alternate Mixes
A preferable way to present files is for the mix engineer to include alternative versions of the mix: vocal up, vocal down, solo up, solo down, etc. Remember it is important keep these alternate mixes well marked, organized, and documented.
With the advent of DAWs, one question that has come up is whether it is preferable to have stems as part of the delivery. Some engineers prefer stems to allow more tweaking and flexibility in the mastering process. However, there are also several potential drawbacks to this.
Including stems can blur the line between mixing and mastering. The mastering engineer can start to lose objectivity, because he or she is now tasked with balancing the final mix. Another concern is that the character of the whole doesn’t necessarily translate to the character of each of the stems. In trying to optimize each individual stem, the result is often detrimental to the nature of the final mix.
3. Don’t Over-Compress the Final Mix
Digital audio files should be delivered at the same resolution as the recording. It’s important that the mixes include some headroom to allow the mastering engineer room to work. A good rule of thumb is to have peaks at around -3 dBfs with an average (rms) around -10 to -14 dBfs. Final buss compression should remain minimal, because it's not something the mastering engineer can undo. A standard practice can include final compression of the mixes as a reference file to the artist, but it’s best when that’s not included in the delivered files for mastering. With high-resolution audio there is no advantage to maxing out the levels.
In a related issue, it’s helpful to not have fades included on the final mixes. The mastering engineer can make fades shorter, but can’t make them longer. Sometimes in the sequencing you realize you want it longer than you thought you did, just to keep things flowing properly.
A Note on Loudness:
There’s been a lot of discussion lately about the issue of loudness. There are pros and cons to having high levels, but there’s a point where it can be too loud or too quiet. A misconception about a loud file is that it will sound louder on the radio, when in fact the opposite is true. Going through all the compressors on the broadcast can clamp onto a signal and hold it back. The louder a song, the smaller it will sound on the radio.
Similarly, a misconception about MP3s is that the louder the song, the better they sound. The purpose of an MP3 is essentially to shrink the file size, which occurs by eliminating data. The algorithms are designed to throw away data below a certain threshold. Low-level information is discarded. A highly compressed song has no low-level content, therefore the algorithm is throwing away information you can hear.
4. Gear Is Great; the Room Is Better
The most important piece of equipment for a mastering engineer, besides his or her own ears, is the room. The feedback given by the room affects the perspective and opinions of mastering engineers, which in turn influence the decisions they make. A revealing monitoring environment tells everything about the mix — the good and the bad. This is necessary for mastering engineers to be able to make accurate changes that affect the final translatability of the audio. One of the goals of mastering is to ensure that the project sounds as good as it can on a wide variety of playback systems.
5. Don’t Master Your Own Work
If you are too close to the material, it is hard to emotionally separate yourself from the content, and accurately hear things like level, EQ, and dynamics. This is not because you don’t have the skills, but because it is extremely difficult to have the emotional detachment necessary when you are listening to your own work. An essential role of the mastering engineer is to be emotionally unbiased. The mastering engineer and the mix engineer should be two separate people, in two separate environments.
It is always best if you can involve your mastering house early in the process. Get the specifics for submittal before the final mixes if possible. If they are willing and time permits, submitting your mixes ahead of the mastering session can allow for detection of problems and suggestions for improvement.
Mastering is the final creative step to take your mixes to the next level. The specialized equipment, finely tuned monitoring environment, and most importantly, the unbiased experience of a pro will help you hone your material to a competitive edge.
Following these suggestions can help you enter this final stage with confidence, and help you maximize your time for a smooth and productive session. This will ultimately save you time and money, prepping the way for a productive and hopefully enjoyable experience.
Michael Romanowski is a mastering engineer based in San Francisco. He has many years of experience and has worked with a wide range of artists, including Norton Buffalo, Joe Craven, The Radiators, Too $hort, and Paul Jackson to name a few.
— Michael Romanowski
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