You have two Mac's...
You have two iTunes libraries...
You never have all your songs on each Mac...
syncOtunes synchronizes your iTunes libraries
select the iTunes library file from your first Mac.
open the iTunes library of your second Mac through a network share.
syncOtunes compares the songlistes and creates a folder for each of your Mac's, containing the missing song files.
import that folder into iTunes with an applescript, not needed files are automatically trashed, and you're done.
