ok cool
now, go in to tools>import>configure auto import
select your drive, and edit
select add for "apply these tags"
for field, select your [file group location] field
then paste the expression into the box
now, all your files will self tag when you put them into the correct folders!
edit: i know you had some brackets in there...try this code for some exactness i think it should work
=ifelse(isequal([filename (path)],soundtrack,7),(soundtrack),isequal([filename (path)],1-E,7),1-E,isequal([filename (path)],F-O,7),F-O,isequal([filename (path)],P-Z,7),P-Z,isequal([filename (path)],Various,7),(Various Artists))