Mixing is a very delicate subject, but also a simple one when you look at it in the right mind set, mixing is the art of organizing the levels of a song in volume, panning instruments left and right, forward and backwards with reverb, putting equalizers to give a more or a less robust sound to an instrument, applying compression to everything that the mixing engineer considers, and basically making the recording sound as awesome as possible.
Mixing engineers are very talented and attentive to detail people, the can hear a song and know where everything can be placed, they can assist in taking your song to the next level if you work with a Pro and as a producer, you can deliver your song and the sound you are looking for. To acomplish a good mix there are many different factors that come into play but a good way to jump many hurdles is to have examples of songs where you like the sound, with the vocals, the low end, the high end, instruments, etc, and you can give the mixing engineer some tangible audio examples of what you want, that will always put into perspective and change the final outcome.
What we fail to acknowledge is that many people believe or say, “we will fix it in the mix” and that can be true in a few cases, but it is a mistaken concept, a song is only as good as it’s worst element and if you record something crapy and expect to fix it in the mix, there is only so much plugins can do, so when you are producing you have to look for the best capture possible from the beginning so that the Mixing engineer can focus on what he is there to do which is Mixing, not fixing our recording problems which in turn will bring down the quality of your song.
Once the mixer has the tracks to your song, it will take a couple of days before he sends you a sample in order to get a feel if he is going in the right direction with what you are looking to accomplish, at this point you will be able to make suggestions, corrections or whatever to allow the engineer to arrive at the best possible product. Once the mixing engineer gives you the initial mix completed your responsibility as a producer is to take note of all the changes no matter how small, remember once the mix is done you will have to live with it, so you better make it as best as you can while you have the chance.
After your corrections or annotations are made from the initial complete mix the engineer will proceed to hand you the final mix.
This is an exciting moment because at this point you know you have an 85% to 90% finished song. One of my mentors and an excellent Mixing Engineer who won sevaral Grammys would always say to me,
So as you can see the Mixing is very important but as I will say a million times, the foundation will always be THE SONg, THE SONG, THE SONG.
The next step after Mixing is Mastering.