Section 4.2.2. in Notes on book design makes a reference to mixed portrait and landscape pages.
I am aware of pdflscape, that allows such a mixing, but as this manual is written by the author of memoir I would assume that such a scenario should be achievable also using the built-in capabilities of the package itself.
I am unable to find any references in the main manual, and would appreciate any comments pointing me in the right direction, as I am sure I must have been overlooking this feature.

memoirfor this. Butpdflscapeis compatible withmemoirso there should be no problem with using it. – Alan Munn Feb 25 '11 at 2:46pdflscapepackage is maintained by Heiko Oberdiek, while thememoirclass is maintained by Lars Madsen. – Matthew Leingang Dec 13 '12 at 13:21