Everyone who looks at the credits on a CD will have seen a line for "mastering." But like the "best boy" and "gaffer" credits at the end of a film, few people know what it really means. Oddly enough, many musicians don't even quite get it.

Mastering is the final step in the process of making a CD, before the music actually gets encoded onto a disc. In the old days of vinyl records, the mastering engineer converted the sound on magnetic tape into a physical stamper used to press records. Nowadays, it is the stage where all of the songs are brought together and their levels and tones are equalized. Segues and some effects can be added, too.

There are two people in Milwaukee whose careers are dedicated to mastering: Gary Tanin at MultiMusica and Trevor Sadler of Mastermind Productions. Others do mastering work, but few would argue that these guys are the serious mastering engineers in Milwaukee. They are the ones with experience.

Sadler began mastering when he worked at a now-defunct, big-time studio in Lake Geneva. He has gone on to become a regular mastering engineer for Milwaukee's Narada Records and some of its associated labels and now runs his own mastering suite in Bay View.

Tanin, a musician and producer first, became interested in mastering in the days of vinyl and began to work in earnest as a mastering engineer in the early 1990s. He runs his suite from his home on Milwaukee's South Side.

So, why don't they see more local work? Partially, it's because for most indie bands, the money has run out by the time the mastering step is reached.

"Budget constraints often are a problem. It's a shame to forgo the one step in the process that can make such a dynamic difference," says Tanin. "Ninety-nine point nine percent of all commercial releases are mastered. The reality is, your record will be compared sonically against these commercial mastered releases. If it doesn't hold up to that kind of scrutiny it will be difficult to be taken seriously."

Add to that the confusion about what the process actually entails and voila, you've got countless records that lack a professional edge.

"I think mastering at a professional facility -- and by that I mean one set up for mastering and mastering ONLY -- is an esoteric and misunderstood art form, and I also think most local musicians and engineers don't have the budgets to have their projects mastered properly/professionally," says Daniel Holter of Burst Records. "If they've never experienced it, well, it would certainly be difficult to understand the value."

Sadler agrees.

"Yes, most people don't really think about mastering unless it's brought up by a recording engineer or producer, or they realize their recordings don't have that same "finished sound" as other commercially released projects. Many of my first time clients come to me having no idea what mastering is, just that they need it, and I was referred to them. Even many of my more experienced clients who are familiar with mastering basics really don't know what I'm doing -- they just sit on the couch and trust me!"

On the other hand, many artists arrive in the mastering suite -- which is often little more than an acoustically-sound room with a computer, a small rack of gear and perhaps a tape machine -- with unrealistic, "let's fix it in the mix" attitudes.

"Ideally, the artist brings mixes to mastering that they're completely happy with," says Sadler. "In this case the mastering engineer can concentrate on doing very small adjustments to improve the mixes and get the overall volume louder. In many cases however, the mixes need to be "fixed" in one way or another. This now starts us on the slippery slope of 'fixing it' in the mastering. This is not the position you want to be in: having your mastering engineer 'save' the sound of your record at the last minute."

What are some of the fixes that can be achieved?

"Today many musicians are foregoing the recording studio and creating recordings at home," says Tanin. "In those scenarios mastering very often helps the mixes of those kinds of recordings. Mastering can't fix a bad performance (but) mastering can make a good performance sound better. Things like timing errors and pitch correction on the finished mix are not a 'mastering fix.' If a recording needs more low end or high end, those are things mastering addresses well. Providing a consistency from track to track in a recording, making it louder, adding dimensionality are all well addressed with the mastering process."

Tanin also points to something often overlooked in the mastering process. A trained and objective ear.