You will need both folders "Guitar Track" and "Guitars".
The "Guitar Track" folder has the settings for the stomp boxes and effects used by the special "Electric Guitar" tracks, and the "Guitar" folder has the settings for an electric guitar recorded to a regular real instrument track.
Here's the thing; among all my filters for "Bass", "Drums", etc, "Guitar Track" was its own folder with no "Guitars" folder in sight. The only 37 files in the "Guitar Track" folder were the 37 filter effects that should actually be in the "Guitars" folder, had it existed. This was all nested within the "Real" folder in the path I quoted above. I do have a "Basic Track" folder, but it shows up as one of the 9 effects categories in GarageBand.
No idea - how did you migrate/ install your current version?
I had done all available upgrades as they came from Apple. My previous main computer (among some others) was a 1.25ghz iMac G4 with Leopard, until I moved over to my late 2008 Alu. Uni. MacBook with Snow Leopard. I am now on the latest Mountain Lion with the latest iLife and iWork suites.
I started fresh on the MacBook with Snow Leopard 10.6.3, and moved over my Documents, Music, and other personal files as I saw fit. Time Machine kept everything safe, but as iLife and iWork suites got updated, and as new versions of OS X rolled out, I upgraded along with them, behind by a couple of months for major releases pending testing.
I am now on the latest version of Mountain Lion 10.8.4 - and until today, I just thought Apple removed the guitar effects, as I rarely used GarageBand; primarily because I kept the iMac G4 as my media machine, and I did all my guitar work on that, with the old effects.
So, somewhere in the past 4 years, something went wrong, and it was nothing I ever did. I never played with the GarageBand folder until today. Interesting to say the least.