Updating Music library

I don't seem to be able to find an option to simply "scan for NEW content" on my music library. All that's there is Update Library. When I select that, it scans the entire library (which takes hours), and whilst it does find the new content, it also creates a duplicate of everything that is already on there. So I have to go through this whole procedure of clearing the whole library and then recreating it every time I add something new.

Surely I am doing something wrong here! This doesn't happen with movies. Can someone please advise? Thanks.

Context menu on any folder (i.e. a real folder, not a virtual db node) should have "Scan to Library" or similar.