I get what you are saying but compression does shape the sound. It can bring cohesion to a mix. If I'm to mix the sound I want then wouldn't any further compression to raise the level to industry standard in mastering threaten that original mix?
Yes, you are right that compression, EQ, and many of the other things that a good ME will do does change the sound. I didn't mean to imply that mastering is completly transparent. On the other side of that coin, the goal of a good mastering engineer is usually not to try and create the sound of the mix, but rather to make the mix that is there shine. Maybe a way to state it is that the mix down should bring you 90% of the way home, and mastering will add that last 10%. But don't expect that last 10% to give your mix a character that isn't already mostly there.
Are you an ME? Would you advise me not to over compress my original mix? If yes then how do I get the sound I'm looking for if it's sounding like it needs more compression or cohesion. Again I'm speaking about a hypothetical mix.
I am not a professional ME, 90% of the audio work I do is in mixing. But in that capacity as the creator of the 2mix, I have worked with MEs, and also have made friends of and learned much from many of the pro MEs who do hang out on this board. I'm sure they will check in here sooner or later with their take on all this, and I will defer to them.
But, in the meantime, based upon my experience, the more an ME has to work with, the happier they are. Put kind of bluntly, let them do their job and don't try and do it for them. In short, once the 2mix is done, let them take it from there.
Now, that doesn't mean that you shouldn't do what you can to make the mixdown sound as good as possible. Just the opposite; the better the quality of the mixdown, the better the job the ME will be able to do with it. But that means getting the mixing right. Getting the mixing right means getting the mixown right when you mix it down, not trying to "fix it up" after the fact. Get the tracks to work together by working on them at the track level.
If Instrument X needs compression to get the kind of punch you're looking for, then give it to that track, and then find the best way to fold that track into the mix. But to apply blanket compression to the entire mix because of one track that needs a specific kind of punchup is kind of like firebombing an entire city just to take out one command post
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And remember, when you see U2 or Green Day squarewaving to get volume, there is often more than just compression going on. Often times they will incrementally add layers of light compression, tweaking and adjusting as they go, maybe with a *little* MBC to anticipate the next compression, or with some M/S-based EQing to pull out a track that got a bit buried by the last compression, etc. Then perhaps some hard limiting of just a few dB, and sometimes even some little bit of purposeful clipping through an additional stage of A/D conversion to give that final volume boost (and in the process, chopping off the peaks.)
I won't go into the pluses or minuses or other details of each step in that process, but on that pro level usually (there are always exceptions) the ME goes through all those steps of work not so much to make the mix sound greatly different, but simply to make it sound louder *without* sounding a whole lot different.
G.