The legacy sounds are not a part of GarageBand 10. They have been installed by older versions of GarageBand '09 and GarageBand '11, by the Jam Packs, or previous version of Logic. The method to preserve them is to never make a clean install, that wipes the installed sounds and loops, because the sounds of loops of GarageBand 10 are different.
- Try to recover the missing sounds and loops from your Time Machine backup, if it goes back to the time before you erase the sounds and loops. Look at these folders to find the missing Legacy sounds in your Time Machine backup:
- /Library/Application Support/GarageBand/Instrument Library/
- /Library/Application Support/Logic/
- /Library/Audio/Apple Loops/
- and the corresponding Library folders in your user library in your home folder
Another simple way (but not free) is to get yourself MainStage 3. With MainStage 3 you can reinstall the Legacy sounds of the Sound Library:
MainStage is installing the Sound Library and the Loops in the same directories as GarageBand or Logic. So GarageBand will see them. But not all sounds and loops are compatible with GarageBand. Mainly the JamPacks and compatibility loops and sounds will work, but that plenty of very useful software instrument loops and sounds.
After installing MainStage 3, launch it and use the command "MainStage 3 > Sound Library > Open Sound Library Manager".
When the Manager opens, scroll down to the "Legacy" section and click the disclosure arrow.
select the Jam Packs you want to use. I installed all from the Legacy section.
Click the checkmarks to the left of the JamPack you want and then "Install". The packages are gigantic. You will see the size when you select them. Start with the ones you really want. The download may take a very long time.
After installing the sounds and loops, restart the Mac. Then launch GarageBand and use the command "Loops > Reindex All Loops" from the Loops Browser.
