I recently purchased MainStage 3 with the sole purpose of downloading the available GarageBand Jam Packs. I've researched this question extensively without much luck, but how do you get these instruments into GarageBand? I currently own GarageGand '09, which I don't think should be a problem seeing as the Jam Packs originally released back in 2006. So far I've only downloaded the Orchestral pack to test this out before downloading anything else. I have figured, however, that these instruments seem to show up in Mac HD/Library/Application Support/Logic/Sampler Instruments as opposed to Mac HD/Library/Application Support/GarageBand/. Do I simply take the "Orchestral" folder found in the Logic Sampler folder and move it somewhere in the GarageBand folder? Or is this wrong entirely?
I'm going to bump this one more time. I'd like to make sure that I'm not putting my computer in any danger before I attempt anything that I shouldn't attempt.
Before you do anything with the library files, be sure your backup is current and includes the libraries, not only your documents.
It is hard to answer that question, since most of us cannot experiment with your setup - the latest GarageBand versions are GB '11 and just recently GB 10.0. I don't remember, if the Instrument Library was in a different place in GB '09.
And most of us have downloaded the JamPacks already as stand-alone boxed versions or as part of MainStage 2 . I don't know. if anything changed with the upgrade to MainStage 3.
For MainStage 2 it was sufficient to reindex the loop library. The MainStage 2 installer installed the instrument library, where it was needed for GarageBand '11, so nothing needed to be done.
In GB '11 the Instrument library will look like this, compare to your version - try to match the files you are seeing in the Logic folder to the files you are seeing in GB '09 and copy - don't move them - to the corresponding folders in Application Support > GarageBand.
The Apple Loops, that come with the JamPacks, should be installed in /Library/AudioApple Loops/
(see this GarageBand, Logic: Where loops get installed)
Check, if you are seeing additional Loops in other Folders and rebuild the Loop Index, see Rebuilding the Loop Index in GarageBand