What Is Mastering?

I’m writing this blog post from Rodney Mills’ Masterhouse and thought it would be appropriate to write about mastering. We touched on some terminology in my post about the mixing process (The Mixing Process, and Why I Used to Hate It), but it’s worth elaborating. Half the time we talk to a band about recording, there is confusion about the difference between mixing and mastering.

The recording process is made up of several stages. First, there’s the part where the band calls up and says “hey we want that Wizkid Sound sound” and we tell them it’ll cost five million dollars per track and then we negotiate. After that, we do pre-production , which is explained in Dan’s article. Next, we ‘track’ all the instruments, which is probably what is most commonly associated with ‘recording’. This is where the band plays their songs, instrument by instrument or as a whole, and we capture the sound with microphones. (We’ll be writing more about this in a future post.)

So, now we have a bunch of songs, made up of dozens of individual instrument tracks. In a typical pop rock production we’ll have anywhere from 30 to 60 tracks and each track represents a different microphone on a particular instrument. For example, we usually use anywhere from 10-16 microphones on a drum set, multiple guitar tracks, vocal tracks, and other instruments. I won’t go into any more depth as we’ll be talking more about this later. The point is that there are dozens of individual tracks that need to be assembled into a coherent song. That’s what mixing is.

To explain mastering, I’ll briefly talk about audio playback technology. Most consumer audio devices play audio back in stereo – that is, left and right channels. When you twist the pan knob on your stereo left or right you’re actually cutting the volume from one side or the other. Originally, recordings were mono, which meant there was only one channel. If you listen to a mono track on headphones or on a pair of speakers, you’ll be hearing the same signal from each speaker, whereas a stereo track will have different signals on each side, making the song a wider stereo image. That’s a very basic explanation – check out Wikipedia’s article on Stereophonic sound for more.

The ‘mix’ that we come up with cannot be played on a regular CD player. We first have to make a stereo file out of it. This process, called bouncing or rendering, takes all the tracks and sums them into a stereo file, which is  two tracks (left and right) assembled into one. With the work we do on the mix, the song will sound good on our studio monitors, which are designed to listen to mixes on, but it won’t necessarily sound good on your car stereo or on your iPod.

“Huh? Why not?”

Well, we get all the tracks sounding good, and get the overall sound pretty close to awesome. Then we take the tracks to a mastering engineer to finish the process. Why bother? Mastering engineers have specialized (read: expensive) equipment designed specifically for mastering. This includes equalizers, compressors, limiters, and other processing equipment.

“But why don’t studios do mastering?”

An analogy would be helpful here. Brain surgery takes a lot of specialized doctors to pull off, including a neurosurgeon and an anesthesiologist. The neurosurgeon probably has the know-how to administer anesthesia, but the anesthesiologist is skilled at the specific area. We’re not brain surgeons, or anesthesiologists for that matter, but you get the point [we are rocket scientists however. ed.]. Consider another analogy. Because you can drive a car, you could probably drive a school bus. But you won’t be that good at it. A bus driver will be better than you. Mastering engineers take the stereo file that we give them and make it sound that much better.

There are different schools of thought and preferences when it comes to mastering. Many mix engineers will tell you that mastering is supposed to be a transparent process that simply brings the mix up to a suitable CD volume. Others like the mastering process to add character to the sound. We like mastering to fix up our mix EQ but not much else. Just like there are an infinite number of possibilities when it comes to mixing, mastering can go many ways. See the external links at the bottom for more about the different types of mastering, including the loudness wars.

Mastering used to be a very clear-cut and separate process of getting the mix from studio tape to consumer media like CD or cassette. That’s usually the case still, but burning WAVs to a CD isn’t such a difficult process anymore – most people can do it on their home computers. Mastering also includes putting the tracks in order, and determining how much space there should be between tracks. Again, not a huge issue anymore. Before CDs and cassettes, the mastering engineer had an even more specialized role. The mastering process would adjust different frequencies to make the recording sound better on a record. This isn’t as much of an issue with CDs and digital recordings.

All that said, we do sometimes master recordings for folks who are on a tight budget. For everything else, we go almost exclusively to Rodney Mills. He’s the jam. Check out his Wikipedia page.

More info:

- Wikipedia’s article on Audio mastering
- Wikipedia’s article on the Loudness war
- Wikipedia’s article on Remastering
- Wired’s article about the Metallica Death Magnetic loudness

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