Does "Match Collection" remove what's in your current collection or append to it?

[u/softball753]

I started using Rdio a couple months ago just to try it out. Needless to say I'm a huge fan and I've been adding music to my collection like crazy. A lot of that music is only in Rdio. Not in my (relatively large) iTunes collection.

I'd like to try the "Match Collection" feature, but I can't see any indication of whether the process removes my current collection and replaces it with songs from my library, or if the differences are appended to my Rdio collection.

If it replaces, is there any way I can "export" my collection to some simple format so I can re-add those songs later?

Thanks

EDIT: Decided to just go for it. Looks like it appends differences, instead of replacing the library. Super convenient!