Introduce vestigial copyright page and move instroduction before the contents,
so on A4 it appears on the verso to the content recto. Tunes then start double
page spread on the next page.
Add a \cleardoublepage before the index of first lines to force that to start on
a new double page. This minimises the page turning necessary to see all the index
lines.
A lot of stuff was being duplicated between different page size. Consolidate where
possible, and in particular put as much into a single source file (dottes.tex) as
possible. Making a single Booke is now potentially quicker, as the tune pages
don't necessarily have to be regenerate every time.