I’m asked this question a lot. In fact, I had written and entire FAQ about in on our old website. The truth is, if the individual songs are well mixed and well balanced; the changes that take place in mastering may be very subtle. On two occasions I’ve actually emailed my client back and told them that their album didn’t need to be mastered. It sounded great as it was.
Before we talk about what to expect from mastering, I think we should talk about what the purpose of the mastering process is. Just as you would mix tracks down to make a final song or stereo track, mastering is the process of mixing down the final tracks to make an album or some other collection of audio tracks. One of the key elements of mastering is fixing any kind of EQ anomalies. For instance, it’s not uncommon for songs to get a buildup of energy somewhere between 250hz and 500hz that can cause a boxy sound or noticeable drone. This is usually due to overlapping bass frequencies from different tracks.
Remember, wave forms (sound waves) in phase will reinforce each other at the peaks and create a subsequent gain in energy at that frequency. Just as waves that are completely out of phase from one another will cancel each other out. This is why it’s always important to check that your individual drum tracks are in phase with one another during mixdown. We’ll probably cover how to do that in another blog. But this build up of energy is more easily developed in the low and low/mid range of frequencies because if the nature of lower frequencies in musical scales and where the octaves are divided. For example, a low E on a bass guitar is 41hz. The next octave would 82hz since an octave is a doubling (or halving) of a frequency. Concert A on the other hand is 440hz. The next octave up is 880hz. You can see that the difference in one octave in the lower scale is much smaller (41hz) than the difference in the middle scale (440hz). There’s even more of a difference in the higher scales. The smaller difference in the lower range makes it easier for frequencies to pile up on top of each other and therefore cause EQ issues. Mastering attempts to fix this by using very narrowly notched EQing.
Another key element of mastering is applying gentle compression when needed. Then there is limiting. It’s used to bring all of the tracks up to a standardized volume level while maintaining a consistent volume across the whole album. Most all of these things can be accomplished during mixdown, but usually aren’t because of the additional time involved. As we all know, studio time isn’t cheap. It is often cheaper to send the tracks to a mastering house then it is to pay for the extra studio time.
As a side note, perhaps the most useful part of sending you tracks off to be mastered is having an objective set of ears. If you can, always have someone else master your music. You have been working on this song for what seems like ever. You’re writing, rewriting, and tweaking this note and that. You’ve lived and breathed this song. That being said, there is no possible way that you can listen to it objectively and make the alterations that it needs without being influenced by your personal attachment to the song. Enter the mastering engineer. That is exactly what they will do. They will listen to your songs and compare it only with other recordings of the same genre. Then tweak it to get the best possible sound and bring it within industry standards.
So to answer the original question, what should I expect from mastering? You should expect the project to sound completed. The EQ should sound uncolored and unaffected. It should have good dynamic range, yet still be brought to commercially acceptable volume levels. The stereo field should sound wide but still natural. And all of the songs/tracks should fit together well. They should have a natural sounding gap between them. And they should all be at around the same volume on the RMS meter. In essence, it should have that final polish on it that makes it sound like a finished project that is radio ready.