Only the first title should be converted to from sort to display order. Subtitles don't influence display order, so don't need to be touched. OK, I now have a subtitle with a comma ('Ring the Bell, Watchman'). If it was the main title I'd have to do something else, but it isn't, so for now...

\section{@SECTIONNAME@ tunes}

{\renewcommand{\arraystretch}{2.5}
\setlength\LTleft{0pt}
\setlength\LTright{\fill}
\begin{longtable}{@{}>{\raggedright\arraybackslash}m{0.2\textwidth}r@{}}
\input{@SECTION@-firstlines.tex}
\end{longtable}
}