Seeing your post reminded me that I forgot to reply to your response about Fairport Convention a couple weeks back! Couldn't really think of what to say except to nod in agreement.
Ummagumma is a great album isn't it - definitely one of my favs by the band. Think it's about time I owned it on CD having owned it on tape for over 30 years. I personally think it is their finest from their experimental psychedelic phase.
I also note with interest that instrumental album by Santana. Wasn't aware of this and will duly investigate