Lots actually! The first step is to have a listen to the mix in question to see what we have to work with. I look at overall volume levels and examine the bandwidth of the mix, in other words…, how is the blend of frequencies from Low, to Mid to High? We look for any phase issues from one channel to the other, and when something is perfectly out of phase one speaker will be moving backwards while the other speaker is moving forwards at the same instant. The resulting sound is ear bending, it almost makes one nauseated and dizzy feeling. The entire channel could be out of phase or just a single component of the mix.
The volume and EQ balance between Left & Right channels is examined and corrected if it’s not right. The balance between the Mid & Side information is also examined and adjusted as required. When monitoring these mixes, we listen at both low and high volume levels because various characteristics can appear at different listening levels. Mix clarity can diminish when turned down but mid or high frequencies can be outright painful at loud volumes if they are out of balance.
What about dynamics? The general rule of thumb is that clients want to find that balance between having a loud mix, and yet retain as much of the original dynamic range as possible. If one was cutting a vinyl record, the cutting engineer has very specific limitations as to how deep a groove can be cut into the disc. This limitation is cast in stone and no current trend can change it, period. If you want your vinyl record to be louder you have just one choice, and that’s to turn up your power amp. Please remember this: The Vertical movement of your file’s waveform is DIRECTLY proportional to the Horizontal movement of your speaker cones. If you squash the mix with too much compression or limiting you are automatically squashing the movement of your speakers as well. Not too many people think about that.
So why are the other mediums considered to have this flexibility? The reason is that in digital, the sound does not change as your recording levels approach peak digital levels, but in analog recording the sound does change as it increases in volume, in a good way but digital is very bad when it hits the edge of its capabilities. Analog distortion is nice, digital distortion is not.
Further to this examination and correction of each song, all of the cuts still have to be matched to each other. How do you do that? Once a single track is settled on for its best sound, the other songs, one at a time are compared to it. All methods of listening are applied here, mid info, side info, dynamic range, L/R channel balance, all of it is compared song to song at low volumes and high, in stereo and in mono. This process is what builds continuity into the albums I master.