multiple \scores in a lily-book included file?

[Graham Percival]

scales.ly:
scale= \notes{ blah blah}
\score{ \transpose c'{ \scale }}
\score{ \transpose g'{ \scale }}
\score{ \transpose d'{ \scale }}
\score{ \transpose a'{ \scale }}
-----

book1.tex:
\documentclass[]{article}
\usepackage[margin=1cm,nohead,nofoot]{geometry}
\begin{document}
\lilypondfile[26pt]{book1/1scales.ly}
\end{document}
-----

Only the first \score is printed once I run it through lilypond-book.  I
_could_ split up each scale into its own file, but that would be messy. 
This this a bug?  (I can't see any reason for this to be a deliberate
feature).   Can I pass some option to \lilypondfile[] to make it include
the whole file, not just the first \score setting?

This is still on lily 1.6.6, so I could be missing some recent bug fixes.

Cheers,
- Graham