Yikes! It is alive again!!! This thread is like Alien, or Friday the 13th, or Austin Powers!

It never dies!
Not sure what more I CAN add here. My past posts have covered a bit of ground, and without actually getting into specific stuff that is usually only pertinent to the mix one would be currently working on, anything else is just "you could do this, you could do that", and I could never cover ALL the things one "could" do in a mix.
Maybe I can talk about "crowding the mix" a bit here. This has been foremost on my mind lately because of some stuff I have worked on in the last 6 months, where the client wanted the "wall of sound". They felt that having 6 guitar tracks, snare durm samples layered 4 deep, and vocals doubled and sometimes tripled would make the sound bigger, deeper, and more intense.
I have found just the OPPOSIT! It is usually the "minimalist" approach that seems to bring forth the biggest, loudest, deepest mixes I have done. 16 tracks or less usually!
For the "less is more" trick to work, I feel it is important that you start out with tracks that stand on their own very well. Many people it would seem start double tracking because they don't get the kind of power and depth out of 1 track of something, so they feel that doing 2 or 3 of the same thing will increase the "presence" and "power" of the sound. I have seen many cases where layering has actually made the sound more distant and less powerful! There are many reasons why. One can be that a poorly "doubled" track, meaning one that is slightly out of tune and not dead on in timing can cause a comb filtering effect which will rob the track of it's power. Two, that the actual tone might be really messed up, and occupying a very big sonic space in the overall sound, thus, at mix, you are cutting a lot of "meat" out of the sound to make it fit in a dense mix.
When tracking, it is a good idea to have a VERY CLEAR idea of your production. Meaning, you should know what kind of sound you are after, and how many tracks you are going to dedicate to getting that sound. If you anticipate a very dense mix, you are going to want the sound while tracking to be very specific in it's range. You will need to concentrate on making that track sound in a very specific way. If you plan a more "sparse" mix, you can then track the instruments to occupy a much bigger sonic range. You will NEED for the instruments to occupy a broader sonic range in this case, otherwise you will be digging into using a lot of "tricks" with reverb and delay to make the sounds sort of bigger.
Really, tracking sort of "sparse" and "thin sounding" works out well. If the tracks wind up not being "big enough" for you, you at least have a lot of control using "tricks" at mix to make them bigger. Once you learn some of these tricks, they will come easily to you and you won't waste a whole lot of time implementing them.
Tracking "big and lush" can be problematic. I prefer tracking this way though with stuff like vocal and
acoustic guitar stuff (folk music, and jazz/blues stuff). But again, you really got to get the sound RIGHT while tracking because ensuing EQ and "tricks" in the mix tend to not work out so well at mix time. "Big and lush" should probably be avoided unless you have a very good control room to monitor in. The reason why is that what you THINK is big and lush could be the result of phase cancellation and/or coupling in a poorly tuned control room. Your initial sounds were "colored" by the control room, and you find out later that the sound weren't as cool when you play your mix elsewhere. Sound confusing? It isn't really. Think about it for a bit.
Another thing to think about is WHAT will be big in the mix, and what should be small. You can't have everything "balls to the walls" in a mix and expect good results. If you want big guitars and vocals, that is usually at the expense of the drums. If you want big drums, that is usually at the expense of the other instruments, etc......Yes, you can have a few things "big" in the mix, you just can't have EVERYTHING big in the mix. Not possible! Listen to your favorite recordings with an ear towards what is big and small in the mix. It will become very evident in a hurry when you actually listen for it.
Trying to make everything big usually has the reverse effect. You just plainly have too much stuff fighting for attention! This causes your mix to sound quiet, small, and flat. Making everything sound great while "solo'ed" does NOT translate into everything blending together for a nice, big, lush mix! Not by a long shot. When determining what you want big and small in the mix, you must do this with EVERYTHING YOU WILL HAVE IN THE MIX turned up. The reason I recommend doing a mix with just "faders up" before you get into anything else is because you can then hear what instruments, and more specifically , what PART of an instruments sound is "masking" important elements in the mix. Once you have determined that, you can then worked toward removing unwanted frequencies from specific instruments so it doesn't mask other instruments. This I feel is the first "need to do" in mixing. Skip this vital step, find yourself eventually doing it at some point (if you wind up with a good mix that is...

).
What I can't help anybody with though is telling them what is important to a mix. I think truly, this is the "art" of mixing, KNOWING what instruments to make big and small in the mix to make that mix the best it can be! Sometimes you pick based upon performances. Sometimes you pick based upon what is really cool about the song. Mostly, it is a combination of both!

The skill of doing this well is not easily learned, and only the person mixing can really learn it. I cannot teach people how to be intuitive.
Some people work well with certain styles of music better than others. For example, I don't consider myself to be all that hot with modern rock stuff. But, give me a funk tune and I will mix the crap out of it!!!

But, I get many rock bands who want me to mix based on other stuff they have heard me mix in their genre that they liked. I am saying that I don't feel as comfortable with the rock stuff as I do with funk. So, I relax much faster, and can do much quicker work with funk than rock. I can mix rock well, but it takes me longer. Hell, I have seen engineers that can get the same good mix in rock as I can in half the time because they are more comfortable in it than I am. This is a consideration when I bid job for clients, how long it will take to get acceptable results. So, I guess what I am saying is that you may be trying to mix stuff that you are not good at mixing! Self honesty is important you know!
So, to wrap it all up, it is probably better to track thin if you are doing dense productions, or are in a badly tuned acoustic space. Track big if it is a sparse production, and/or you have a good acoustic space. But ALWAYS have a PRODUCTION GOAL. Without that, you are whistling in the dark!
Ed