Okay, the part from about 1:30 to 1:45 isn't from the Six Wives album (although I've heard live versions that varied a good bit from the album), but at about 1:45 he goes back into the Six Wives, then at about 1:50 he goes back into the new bit, mixing it in with the bit from the Six Wives-- so I'd say it's all improvisation based on Six Wives. I'll have to listen to the CD later to get the name of the piece, but it's one of my favorite selections from the Six Wives because of the way it blends the old-timey Old West piano sound with the other musical themes.
None of it sounds like Brain Salad Surgery to me, but it's reminiscent of parts of the Jeremy Bender/The Sheriff medley on the "Welcome Back My Friends" album-- Keith more or less throws in a bit of everything plus the kitchen sink.