Ensure tune graphic is confined to a single page. Set a maximum height for the graphic of 0.9 text area as well as the current target width of the text width. And also keep the aspect ratio. So if the height is small enough, you get full width. Otherwise the graphic is shrunk enough to keep it all on one page. Perhaps one can then go back and edit the tune to fit it into fewer lines.

%
% Take the A5 landscape dottes.pdf and produce a second PDF
% formatted for A4 portrait, which two pages per A4 page,
% and ordered for booklet printing.
%
% Print the resulting PDF with long side duplex.
%
\documentclass[a4paper,final]{article}
\usepackage{pdfpages}
\usepackage{ifpdf,ifxetex}

\begin{document}
\includepdf[pages=-, nup=1x2, booklet=true]{dottes.pdf}
\end{document}