Perhaps predictably I'm finding the variation very enjoyable and the majority of this very appealing; it could turn into one of my favourites from this thread. Don't think I appreciated how much I like the duo format.
In terms of ones that didn't make the grade for nomination beyond Sam and Dave (and btw
@Coatigan that is a great way to close the playlist) amongst others, I decided against great records by acts of diverse as The Civil Wars, Nova Twins and Yazoo (I suspect I'm alone in thinking they are up there as the great lost duo of pop!) but I've done two of those three recently anyway.
The Nova Twins I was going to post for a when is a duo not a duo type discussion (does a shopping trolley full of pedals and workstations count as a third band member like Winston in OMD?) and the difference between predominantly studio duos and live 'proper band' duos.
Anyway suspect it will be easier to list my dislikes than likes but I'm not a fan of doing that.