Since TreeHugger started we have been covering what we call transformer furniture, designs that serve multiple functions and transform from one to the other. Over at Apartment Therapy, they call them Metamorphic Furniture: The Original Small Space Solutions. They have found some pretty wild ones, like the sofa that turns into a ladder for getting to books you cannot reach.
I was not sure about their use of the word Metamorphic vs Transformer. While metamorphosis has been defined as "a complete change of character, appearance, etc" or "A transformation, as by magic or sorcery," Metamorphic is almost always used as a geological term, where igneous and sedimentary rocks are converted by pressure and heat into new kinds of rocks. It's not reversible.
Yet that is the term Christies uses to describe the settee, and a google search reveals that it's pretty common in the furniture world; there is even a pinterest board on it that I am going to loot like mad for the next few weeks. When it comes to furniture, they may be right and we may have been wrong all these years- in academic circles, it's clearly metamorphic.
Apartment Therapy also shows a different version of a piano that turns into a bed. Given the weight of a piano, this is a pretty surprising design.
I think the version we showed earlier is more logical, where the bed pulls out from under the piano.
See more at Apartment Therapy, and here is a roundup of our old antique
And these ones I saw in Paris a few years back:
I think it is more elegant than Benjamin Franklin's that Apartment Therapy shows.