I came up with this version of a concertina binding that builds a rounded spine into the actual structure of the book. I may not be the first person to have arrived at this idea - please let me know if you've seen something similar.
Traditionally, rounding and backing a book with a backing hammer creates a curved spine that fights the natural pull of gravity on the pages of a book. In this binding, there is no need for a backing hammer. Instead the concertina's folds are engineered to create a rounded spine. The concertina binding is already a great structure for albums because the concertina folds act as natural spacers between pages, allowing for expansion of the textblock as photographs or other materials are added. It is also one of the few book structures that allows pages to open flat. The addition of the built-in round creates an added benefit.
I'm including a few pictures here that briefly illustrate the concept, including a diagram for making the folds for the concertina. If anyone is interested in a full tutorial, let me know and I'll start working on something. Keep in mind that to make the round as symmetrical and gradual as possible, one needs to be able to make accurate folds within 1/32" (she says casually). I'm also interested in how this basic concept can be used to create more artistic, not round, asymmetrical structures. I'm playing around with those ideas now.