One simple step you must take to make sure your masters sound really great
It's a plain fact of life these days that if you want your recordings to sound like commercial releases, you have to put them through the process of mastering. A simple mix is no longer enough. But you have to be sure about what you want to achieve.
Clearly you will want to increase the subjective loudness of your mix. There's a loudness world war being fought and if you don't engage in combat, you'll be wiped out. Think of it this way - someone has downloaded your track and has put it into their iTunes playlist. They are listening on their iPod on the subway on their way to work. Of course they have set the volume of their earbuds at a level they like, that hopefully doesn't inconvenience other passengers.
And then your track comes up...
If it seems quiet in comparison to the previous track, this potential fan has to reach into their pocket, take out their iPod and turn up the volume. But it's more likely they will simply skip to the next track. Or do nothing and make a mental note to remove your track from the playlist when they get home.
It is a fact that louder = better, or is perceived as such by many. You can't get away with a track that is quiet in comparison with commercial releases, so you have to master for subjective loudness. (And while you're doing that you should consider giving your track a similar frequency balance to commercial releases, so that it doesn't sound either weak in the bass or excessively edgy in the top end.)
As well as achieving the expected degree of subjective loudness, you might want to make your track warmer. Or apply harmonic generation techniques, which means the same thing. Basically you are going to add a controlled amount of distortion. You might prefer a clean sound, but that's not what the market expects these days, although clearly the amount of added warmth depends on the genre of the music.
If your track lacks the expected degree of warmth, your iPod listener will find your music lacking in excitement. Their playlist is full of tracks that have been warmed up to a lesser or greater extent - mildly toasted or seared in a nuclear furnace. If your track is lukewarm in comparison, then the level of excitement drops. As does your track from the listener's playlist.
The acid test
I noted earlier that 'louder' is often perceived as 'better'. It is difficult even for an experienced engineer to be objective about this. And as the various processes of mastering are laid on, the track will of course get louder. That is entirely half of the point of mastering. So as you work with your equalizers, compressors, harmonic generators, limiters and soft clippers, while reciting magical incantations, your track will get louder. And you will think it sounds better, because it is louder. You might compare it with the original from time to time as you work, but because the mastered version is getting louder and louder, you might think that it is getting better and better. But it may not.
What you need to do is this...
When you have reached a stage in the mastering process where you think you are making positive achievements, bring down the level of the master so that it is subjectively the same level as your unprocessed mix (one way to do this is to have the same stereo mix on two tracks, and perform the master processing only on one of them, then you can easily flip back and forth between the mastered and unmastered versions).
When your raw mix and master can be played back at equivalent subjective levels, you can properly judge whether or not you are really making improvements. If your master sounds better when compared like this, you're making progress. Now go and make some more progress, until you can't squeeze even one more drop of extra juice from your track.
In summary, if you don't compare your master with the original mix at equivalent subjective levels, you don't know whether you're making improvements, or whether what you are doing is damaging the overall sound. Make this simple comparison and you will know for sure whether or not you're headed in the right direction.
P.S. Mastering can make your track fuller, stronger, and more closely comparable with commercial releases. Or it can really mess things up. Take care.