Though no expert, I have found Live versions to be sometimes slightly, sometimes significantly different but regularly longer than the album version of the same song. Perhaps during a Live performance the players are more relaxed or more into the "groove" of the piece and are able to just jam away if the feeling hits them. Or if the audience is sympathetic to their ad hoc noodlings, they'll be inspired to further excesses.

Also, unless a piece is to be an album-side suite like Echoes or Atom Heart Mother, they have to exist on an LP with other tracks vying for track time. Depending on the music company's criteria or that of the players themselves, who can guess what might have been included or omitted?

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