Rjames graciously allowed me to contact him and he very patiently explained to me his setup of Logic 6.3 with GPO. I thought I should share it with people here for future reference (Rjames: let me know if this is all correct! :-)):
Instructions for using GPO with Logic 6.3.3:
In arrange windows, click on AudioInst 1. To far lower left of screen, in the box above “Output 1-2”, click and hold. Scroll the mouse to the right and choose “multi-channel – audio units – Garritan Personal Orchestra”. An instance should load.
Double click on the arrange window track name “AudioInst 1”. This should take you to the Audio window of the environment.
In the box to the far left, click on the name “AudioInst 1”. This should highlight the box, allowing you to re-name it. Give it a new name. You may want to consider organizing your different instances of GPO into sections (GPOStrings 1, GPOStrings 2, Woodwinds, Brass), etc. not only for organization sake, but because this is supposed to use less system resources (since certain patches from within a group share the same samples).
In the menus for the actual audio environment window, you should see “New edit view options”. Click on New, then scroll down and choose “multi-instrument”.
Drag this newly created multi-instrument to right below the audio instr 1 channel you created (which you’ve presumably since re-named). Click and hold on the right arrow in the upper right corner of the multi-instrument; and connect the cable to anywhere in the audio instr 1 channel. Choose “remove” when prompted. Then in the multi-instrument object, click on channels 1-8 so that they no longer have lines through them.
Click on the top of the multi-instrument you created (ie. Not on any of the specific channels). To the far left, make sure that the info window’s “Cha” is set to “All”. Click on the top of the multi-instrument you created again; to the far left’s corresponding window, click on the name and re-name it to the same name you re-named it to above.
Go back to the arrange window. Now click on a free general midi channel (or another channel). Click and hold on the name, scroll to audio ‡ and you should see the name of the audio instrument you re-named listed here; select which of the 8 channels you want (you should probably start with 1).
SHORTCUT: use the arrange windows submenu (“edit functions audio view” to choose “function – track-create with next instrument” and the next appropriate instrument within this instance of GPO will automatically be created in the arrange window, until you’ve created all eight slots for that audioinstrument instance).
From the arrange window, click on the original audio instrument you created. This will take you to the audio environment window. Now click on “Garritan personal” above “output1-2” to open up that particular instance of GPO. You can now add separate patches and fill up all 8 slots as needed.
Repeat all of the above steps for each subsequent instance of GPO you want (start with audio instrument 2 in the arrange window to create the next instance of GPO, etc.).
You can also create separate effects for each INSTANCE of GPO (which is one more reason it makes sense to group according to sections, since they would all generally require roughly the same EQ levels). If you want (for ex) a solo instrument to have a completely separate VERB level, then put it in a completely separate instance of GPO.
To create effects, click from the arrange window on the name of the original audio instrument (which you’ve now renamed) (ie. NOT the ones you converted from general midi channels).
Under “Sends” in the lower left, click and hold the first box and choose bus 1.
Double-click on the original audio inst. name in the arrange window in the track listing to take you back to the audio environment window. Double click on “bus 1” for your audio instrument; this will take you to the bus 1 track in the audio environment window. In the bus 1 track, click and hold the first box right below “insert” and choose “space designer” (or another verb plug-in).
Go back to the arrange window. Make sure the audio inst. you re-named is highlighted. Look in the lower left. Set the level knob to the right of bus 1 so that it’s at “0”. You can then adjust it up or down from here to set reverb for all of the tracks under this entire GPO instance.