Sorry about that link - must've copy / pasted the wrong URL.
Anyway, if you use a Time Machine backup or Migration Assistant to move your data from the old Mac to the new one, you might not have to mess with any settings at all.
@grinnell: I don't want to import anything to the (hypothetical) newer mac - I just want my 'itunes library' (which is on a HDD) to show up in the 'music' app when I connect the HDD to the (hypothetical) new mac. I'm kind of hoping someone here's gone from a mac that has the 'itunes' app to one with the 'music' app, and, like me, has all their music on a HDD.
I suspect @yage is right that it won't be an issue, but it'd be nice to know in advance.