song as one instrument in order to equalize it properly -- I know, it can be quite hard, especially since you have to analyze and set up every single track in a proper ratio to the others. As I wanted every single instrument to sound warm and full I almost every single time added a certain amount of low mids to middle frequencies (in the range of 200 to 500 Hz -- that's the critical point). Unfortunately these frequencies, if they're accumulated much, tend to make the song sound 'blunt' and kind of stuffed full with 'non-brilliancy'.
I made the experience that it is advisable to take out a certain amount of these frequencies especially with guitar, vocal, and synthesizer tracks, and to instead add these to bass guitars and bass drums.
Nohow would you want to take these completely out, but you'll be astonished how full and balanced every single instrument sounds in the general view by reducing and shifting specifically low middle frequencies.
One more thing: Earlier I had been using loudspeakers that used to emphasize the high and low middle frequencies. Using non-linear loudspeakers can be a great issue with mixing your songs -- back then I thought that all my master bounces were great and brilliant, but when I listened to them through linear loudspeakers the bounces sounded 'as dry as a bone'. The ultimate key with monitoring songs is to firstly make them sound great through linear loudspeakers and secondly through non-linear, maybe even trashy ones.
Take An External View
There are some things anyone who is too much involved in mastering a song can easily misjudge.
It can be a big mistake, for instance, trying to make all instruments sound equally loud -- that doesn't really work. Well, actually it does work and it's possible to make all tracks sound equally loud, but it's probably not what you're really looking for. I tried this myself and had to realize that it would pose more difficulties than it would solve problems. The big issue about this is that the listener doesn't know on which element to focus and this makes listening quite taxing. Best, you create a mix that makes perfect sense to the listener and to which they can simply 'abandon themselves' without focusing.
The key is to so to speak allot a leading role to one particular instrument group and then to emphasize certain elements of this group. As soon as you have chosen a group to 'play the leading role', note that it is exactly the same important to also decide what particular element of the group shall undertake the leading role here. With drums I would always put the snare and bass drum into the foreground, with vocals you would probably choose the lead vocals and reduce the volume level of the others, and with let's say two guitars you'd pick the lead guitar or, if there is none, the one that has more high frequencies or so. It's the exact same thing as the golden section in painting.
