Hello ironmist,
Welcome to the Apple Support Communities, and thank you for the details of the issue you are experiencing with the software instruments in GarageBand.
First, I recommend starting with the steps in the following article:
Logic Pro X, GarageBand for Mac (v10.0): Reindex to fix issues with Apple Loops
http://support.apple.com/kb/HT5894
If you still do not have access to the software instruments, I recommend reinstalling GarageBand. Use these steps to uninstall GarageBand:
Uninstall apps
- To uninstall apps you purchased from the Mac App Store, hold down an app’s icon in Launchpad until all the icons begin to jiggle. Click an app’s delete button (x).If an icon doesn’t have a delete button, it can’t be uninstalled. For example, apps that come with OS X can’t be uninstalled.
- To uninstall other apps, drag the app to the Trash (located at the end of the Dock), then choose Finder > Empty Trash.If you change your mind, before emptying the Trash, select the app in the Trash, then choose File > Put Back.
OS X Mavericks: Install, update, and uninstall apps
http://support.apple.com/kb/PH14299
Then, you can redownload GarageBand from the Purchases pane of the Mac App Store.
OS X Mavericks: Reinstall apps that came with your Mac
http://support.apple.com/kb/PH14193
Best,
Sheila M.