I own a Edirol PCR Midi Keyboard Controller and am trying to figure out if the knobs and sliders can be programmed to different GarageBand functions and can't seem to find a straight answer anywhere! When I asked an Edirol rep if they were going to come out with a control map for GB I was told no because GB has no Midi control support. Wouldn't it have to have some sort of support since I can play notes and use the bender? A member of the Apple forums said that he was able to do it with the PCR Editor and wrote: I figured out how to remap common control commands to the knobs and sliders using the PCR Editor!
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Channel Mode Messages

The last voice message is Control Change, and these are specifically linked to the Channel Mode Messages. When a Control Change message goes out, it is specifying one of the 128 different Channel Mode messages, which globally direct specific functions of the data.  The most important ones to remember are #0 (Voice Bank Selection), #1 (Modulation Values), #7 (volume), #10 (panning), and #64 (sustain).  Controllers 120-127 are also very important, for they specify the mode of the keyboard.  These are All Sounds Off (# 120), Reset All Controllers (#121), Local On/Off (#122), All Notes Off (#123), Omni Off (#124), Omni On (#125), Mono On (#126), and Poly On (#127).

I tried doing this myself but had no luck being new to midi. Does anyone know if he is correct and this can be done? I'm actually interested in using the knobs and sliders for different functions but these maps would just change the sound? If anyone can tell me the exact midi capabilities of GB I will be forever grateful! Any feedback greatly appreciated! Please help!