One of the common questions I get is “If a mix is really good, then why would mastering be necessary?” And that’s a valid question, because if the mix sounds good, then that’s all you should need…right?

In theory, doing a great mix would eliminate the need for mastering. But this is rarely the case; the analogy I’d use is putting dressing on a salad. You could put a certain amount of dressing on each piece of lettuce, tomato, etc.; when combined, you should have the same results as putting dressing on the entire salad. This would be like optimizing every track, and assuming that when put together, something would sound “mastered.” But in my experience, salads are best when tossed, and I’ve never heard a mix—no matter how good—that couldn’t benefit in some way from quality mastering.

The main reason for this is that when you mix, you’re working on individual tracks to create the best possible blend of all the sounds. But when you master, you’re listening to that blend, and determining what needs to be done to make the composite sound better—not just the sounds of the individual tracks.

For example, suppose the overall sound is just a tiny bit dull. When mixing, you’d have to listen to each track and increase the brightness a little bit on each one to produce the desired result—and even then, you might make one track too bright or one not bright enough. When mastering, you can add a little brightness to the overall stereo (or surround) mix, thus influencing all instruments. If you add a slight high-frequency boost, you’re doing the equivalent of adding that boost to all tracks in the music.

Then again, it’s also true that the better the mix, the more likely it is that the mastering will turn out better as well. It won’t be necessary to add as much processing or do “salvage job” mastering, where the task of compensating for problems in the mix fall on the mastering engineer. In one tune I mastered, the guitar was slightly out of tune, and I was asked if that’s something I could fix in mastering. Sorry! I can’t just magically extract a single instrument from a stereo mix and then fix the tuning. Well, at least not with today’s technology.

No matter how good your mix is, there’s always room for improvement. Many years ago, before I started doing my own mastering, I had a CD mastered by ace Nashville mastering engineer Randy Kling. He said the CD hardly needed anything, but he was able to pull back the highs in a few places to reduce some hiss, and added a bit of limiting to make the tracks jump out a little bit more. Were the results radically different? No. Was it worth it? Absolutely—those subtle touches added just the right amount of “seasoning.””

However, do remember that mastering is not intended to salvage a recording, but enhance an already solid mix. If there’s a problem with the mix, remix the tune—don’t count on mastering to solve the problem (although I’ll certainly give it my best shot!).