When you're listening to the title track of "Atom Heart Mother", at about the eighteenth minute, the vague keyboard notes sound very much like those at the first minute or two of "Echoes" from "Meddle."
At the beginning of "Fat Old Sun" from AHM, you can hear bells in the distance--they sound exactly like those at the beginning of "High Hopes" from "The Division Bell."
Maybe the Floyd did this on purpose, I don't know. Any thoughts?