CC stands for Continuous Controller, it's a type of data message that allows knobs/button/faders ect, to be interpreted by your software, and in turn control the assigned parameter.
I wrote a peice on Akai and midi for some other guy recently, it's a long one, but might be of some help.
http://discussions.apple.com/thread.jspa?threadID=2687667&tstart=0
You can control a variety of features of garagband with your LPD8, you just need to adjust the CC values of the knobs with the editor software you got, and know what cc controls what.
By default, knob 7 will control volume yes? This is because it's default cc is 7, which is recognized by Garageband to adjust volume. By adjusting the LPD8 cc controls to the correct cc messages recognized by Garageband, you will be able to control several more parameters.
Although gjmnz was right, the midi applications of Garageband are very limited, and a midi mapping feature would be invaluable.
Here is a list of the only midi controls recognized by Garage Band. The items with a "*" can only be controlled with a button (or one of your MPK's pads if send to CC mode) and the items without can only be controlled with a knob/fader/encoder ect. Also remember these will only control the track that is currently selected.
CC#3 - Track Solo *
CC#7 - Track Volume
CC#9 - Track Mute *
CC#10 - Track Pan
CC#28 - Echo Send Level
CC#29 - Reverb Send Level
CC#59 - Effect 1 on/off *
CC#60 - Effect 2 on/off *
CC#61 - Effect 3 on/off *
CC#62 - Effect 4 on/off *
CC#63 - Effect 5 on/off *
Message was edited by: andrew_langdon