Simply put, in the Aria Player Mixer View you will see the following:
Control 7 moves the individual instrument channel sliders for mixer Volume Control. This is the same as setting the Mixer Volumes.
Control 1 controls the Modulation Wheel. You can see the Mod Wheel at the left end of the keyboard on the Aria Player Mixer screen move as you move your mod wheel up and down.
Control 11 is the same as Control 1 but you can assign control 11 to let's say an expression pedal for operation with your foot. The same as a volume pedal.
Aria is hard-wired to your Mod wheel for controlling volume.
In Sonar I set the midi channel Volume to the loudest mix level I want that instrument at. I then turn on the Automation Lane for that channel and set it up for Control 1 or 11. The automation lane is where I do my actual mix moves for that channel. In other words, The Channel Volume in the midi part is like a Master Volume, set it and forget it. Now when I do my expression adjustments they are done in the Automation Lane.
I learned a long time ago that most DAWs use control 7 for channel volumes and 11 for expression. Working the way I just described will save you some headaches if you move between DAWs to work on the same project.
If you mix using control 7 only, there's going to be a good chance that you'll have to re-mix just about every track!!!
But, if you use control 7 for your channel volume and use control 11 for your mix moves when you import in to another DAW you will PROBABLY only have to change Control 7 because your mix moves are all separate and still there! In would rather have to just turn the track up louder or softer and keep my mix than have to edit the WHOLE track over.
If your a guitar player or do any mixing at all it's easy to look at it this way. Control 7 is the volume on your amp, set it and forget it. Control 11 or for Aria, control 1 is the volume on your instrument that you turn up and down as you play to blend in the mix.
I didn't mean to get long winded about this but it is quite confusing dealing with Garritan and these controller numbers. I hope this helps you to think of it in simpler terms. Good luck!!