A mastering engineer makes the final adjustments to audio material so that it is optimised for most playback scenarios. Fundamentally, a mastering engineer needs an accurate and familiar place to listen to audio content and a way to process audio such that the necessary adjustments can be made to produce the master. In this discussion we will imagine the simplest mastering setup, utilising modern digital technologies. Of course a mastering engineer may work in a complex and equipment-heavy studio but the basis of any studio is an accurate monitoring system and some way to process audio.
Monitoring
There are a few things to consider here; why do you call it a system and what’s in this system? and, what is accurate? We refer to a monitoring system because we are talking about the combination of equipment that allows the information in the source file (.WAV audio file, for example) to reach the mastering engineer’s ear and be perceived as sound. The system is greater than simply a pair of speakers or headphones. In the most basic, modern scenario the monitoring system would be the computer (where the digital music file is sitting), the digital to analog converter (that converters the information in the digital file to an electrical signal), the powered speaker (which converts the electrical signal to acoustic energy), and the listening environment (the room your in, filled with air, that transfers the acoustic energy to the listener). These elements are working together to present the auditory experience to the mastering engineer, and all these elements have a role to play in the accuracy of playback.
The more accurately this monitoring system reproduces audio material the more confident the engineer will be that the work they are doing will be of benefit to the mastering project. But what do we mean by accuracy? There is perhaps a theoretical definition in which if you could record a performance with 100% accuracy and then play that back over the monitoring system the resulting experience would be sonically indiscernible from the original event. In literal terms this is near impossible to achieve and nearly impossible to test, somewhat reinforcing the impossibility of the completely accurate monitoring system. Luckily, the impossibility of this goal of accuracy has not prevented great development in monitoring technology and there are many ways to achieve a great system that will allow you to produce great masters. A more realistic goal for a monitoring system could be that when the digital source file serves up information that instructs the system to produce a certain frequency, at a certain amplitude, and at a specific time, that same set of parameters are perceived by the listener. The closer your monitoring system can be to interpreting and carrying out the instructions of the source file the greater accuracy we can ascribe to this system.
So, the monitoring system allows the mastering engineer to hear music as close as possible to the instructions that the source file sets out and every element along the system plays a role in influencing the accuracy of this information translation. This begs the question, can anyone with the best/most accurate monitoring system master a recording to the highest degree? Maybe, if they really got to know that monitoring system. Which brings up another important point, knowing the monitoring system.
Knowing their monitoring system is one thing mastering engineers do really well, they listen to the same monitoring system day in and day out for many years. They build up a detailed mental sonic imprint of how audio material is presented on that system. Whilst it doesn’t sidestep the need for accurate monitoring, it does take an accurate system that bit further — to where that small bump at 200Hz, for example, doesn’t prevent us from making a great master because we’re aware of it and accomodate it, intuitively. To summarise, the mastering engineer looks to put together the most accurate monitoring system they can and then gets to know that system thoroughly, through years of listening.
Processing
The second thing a mastering engineer requires is a way to process audio material. If you’re working with digital audio files the simplest way to apply processing to them is by hosting the files in a Digital Audio Workstation (DAW) and using software (known as plug-ins) to run within this DAW and process the digital file. You can use typical DAW software to master a digital file, such as Pro Tools, Logic Pro, Studio One, and Reaper (there are many more). There are some DAWs that are designed specifically for mastering and they offer some additional feature and ease of mastering workflow that the typical DAWs do not. Mastering focused DAWs include Wavelab, Sadie, and Sequoia.
Audio can also be processed in the analog domain, in which the electrical signal which generated the audio is passed through a hardware unit and the output of the hardware is recorded back into the computer. If you’re working with digital files you’ll still need some kind of DAW or software player and a digital to analog converter to make this happen and you’ll also need an analog to digital converter on the recording side of the unit. Audio processing, whether it be analog or digital is a dense subject, so we will leave it for a future blog post.
So, what does a mastering engineer need? A way to accurately hear the audio (a monitoring system), and way to process the music (a computer and DAW). Being really familiar with your monitoring system is key, and having a DAW you’re comfortable using will make the mastering process smooth.