If you mean that you want to independently clean up the iTunes library on the external drive before combining them, no problem. Hold down the alt/option key when launching iTunes and it will ask you to choose the location of the library you want to use. After choosing the iTunes folder on your external drive, wait for everything to become available and then quit iTunes. When you launch Song Sergeant, it will relaunch iTunes and work entirely with the external library.
Use this method again to re-choose your normal library when you're done.
The most important part is quitting out of iTunes after choosing the new library, so that it will store its new settings. Otherwise, 3rd party software like Song Sergeant may get confused about where your currently chosen library is.
Last edited by beastie
on Wed Oct 05, 2011 2:07 am, edited 1 time in total.