What is Mastering?
Was there always a function called audio mastering? With special boxes and super speakers, engineers hunched over a myriad of dials and knobs, in strange rooms with peculiar wall and ceiling coverings, magically making the music sound amazing? The short answer is no: It's a history of time and tricks — and ultimately hands-on experience combined with cultivated expertise — that led to audio mastering. And through that evolution, quality equipment has become paramount for mastering engineers to deliver their #1 goal: make the music sound its best everywhere.
Going back to the very first recording sessions, live players gathered in a room and performed a piece of music while the ‘recording engineer’ made sure a mechanical lathe cut ‘grooves’ into a wax or soft metal cylinder (circa1880-1910), and eventually a lacquer disc (circa1910-1950). Imagine a small jazz band and a singer in the 1920’s huddled around one or more large ‘horns’ that transferred the sound energy from the band to the cylinder or disc (these horns were like the old “Gramophone speaker” on a record-player — remember there were no microphones yet!). Once everyone got it right —the players and the engineer — then recording was done. One take. No editing. No ‘mastering’ involved. The recorded medium was used to create consumer versions in a mechanical copying process.
In the 1940’s recording technology took a giant leap and reel-to-reel tape recording took over in the music studio. While the delivery medium was still a ‘record disc’ on vinyl, the consumer disc was not only a different format as what was being recorded onto, but was the result of a multi-stage process: The mixed tapes needed to be cut onto a laquer disc for each side (A, B, etc) using a record-cutting lathe, then shipped to a metal plating facility where plates for each recorded side of music are created, with the final consumer record disc being "pressed" from these metal plates onto vinyl discs which were then distributed to consumers.
All of this required special expertise passed down from one engineer to another directly with hands-on experience. Careful listening, set-up and literally watching and adjusting the record lathe at work cutting away the lacquer grooves are an extremely critical processes; Almost a lost art, but fortunately not quite.
Every medium has their limitations, and it was the limitations of the vinyl medium that created an opportunity to birth the mastering industry. For vinyl, the fidelity of the music recorded needed to be ‘tamed’ to fit and playback correctly on the lacquer disc master. Loud dynamics needed to be compressed and the spectrum of tones equalized so the grooves were not too large. Why? While larger grooves allow more bass and louder sounds, they can easily cause skips and other playback problems. Processing like EQ and compression were already in use through radio broadcast for many years, so audio mastering engineers embraced these tools and techniques to improve their own results. So it was in the late 1960’s that Lee Hulko at Sterling Sound helped pioneer the idea that "Mastering could be an industry unto itself." As we saw previously, recording studios would purchase a Neumann, Skully or Presto disc cutting system that included a tape machine, a little console, EQ and compression and had a ‘studio assistant’ prepare the discs for duplication — but it wasn’t a formalized process like mastering has become today. Hulko innovated the idea that after the recording session, he could play the tapes in a special room and work with EQ and compression rather than just having the tape transferred to disc so the record wouldn’t skip. Thus Mastering became a separate step in the recording process altogether. What began as an assistant transferring tapes to disc became a separate industry of dedicated professionals with tools, techniques, and studios unique to their role in the recording process.
When a mastering engineer can truly hear what a recording contains – and today that means mostly what the ‘stereo mix’ of the music tracks is — they can make decisions to use their specialized equipment to bring out the best that exists in the mix and balance it so that any playback device (home hi-fi, car, iPod, etc) will offer a fair expression of the music.
In typical audio mastering studios today, a digital mix is played by computer, through a digital-to-analog converter, then to a transfer console which has switches to insert various gear, (EQ, compressors, etc.) into the signal path for mastering treatment. Next the audio goes to the monitor control for listening, and finally the signal is sent to a capture platform (another computer, vinyl lathe, etc) for prep & delivery on the target medium being mastered for. The mastering engineer must analyze the source signal via his/her ears and other measurement tools at the studio and decide what processing/treatment is required to bring the track to its full potential. That being said, it is imperative to monitor this signal in clinical way, free of any sonic imprint or "color" the gear may impart onto the signal (tubes, etc) before processing. Obviously ‘color’ can be added at-will with compressors, equalizers and such when inserted into the processing signal path, but key components like the transfer console, DAC, analog summing and monitor control must be transparent to serve the mastering process rather than challenge the engineer with unwanted changes to the source signal that must be mentally compensated for.