So does that mean you can put your mastering applications in to one of the aux busses and use an envelope to apply the plug ins. Wouldn't that be confusing to the mix to add them to independant tracks or can you group those fx envelopes?
hmm, i think your confusing terms a little there man. your aux busses are for send effects during mixing, and you wouldnt want a situation where you sent every track to one bus and then used that as the desks only output, far too confusing!
also, an envelope is something that generates a change in a parameter over time, often something like volume, using attack, decay sustain and release controlls or similar. its not used in mastering, unless you count the attack and release functions built into a compressor which could be considered an envelope of sorts.
all DAW's ive used have a seperate channel, that allows you too add effects to a specific output of your soundcard. in a standard system when there is only 1 output of your soundcard that you are using before speakers (as opposed to using a desk for mixing down,m where you would use lots of output channels) you would apply the effects to this track.
for example in cubase, to the right of the mixer is (provided its not set to hide) a channel which relates to the sum of everything coming out of your soundcard and going to the speakers. this is your master channel or bus and you can add effects to it in the usual way, except any effect you add is affecting the whole mix.
bear in mind though, that mastering is usually done seperately. if you mix, put on some mastering and then decide you want to change the volume of a single track then you would have to remaster. as the changes you make will drastically effect how the mastering compressor responds, changing the balance of the whole thing.
much better to mix, get happy with it and then master seperately to remove the temptation to change mix elements when you are at the mastering stage! they are seperate processes, and it is very very hard to properly do them simultaneously!