There are a couple songs on Ummagumma I love.
Grandchester Meadows is too difficult to hear. The Narrow Way is pretty dull.
But Sisyphus, the Richard Wright selection, is wonderful. It is a slow build, watching in my head the struggle of the mythic figure, his success and failure. Perhaps it is a little long, but I love the long play.
https://youtu.be/Jpo35OqasTkThe other I would post is Several Species, which jdc posted above. I find it playful, like Bike from their first album. The production and engineering is great, and it is Roger at his most humorous.
I had a friend who hated this song. He said that when he was young his brother tied him up to a chair in a basement, turned the stereo so high it was barely tolerable, and played this song a number of times. All he could think about is rats running over his feet and strange men approaching him, speaking harshly. That was not a playful context.