# Formatting the index from the songs package

I've been using the songs package to generate songbooks. I've been tweaking the package for my needs, but one of the remaining issues is the \showindex command. Consider the following code:

\documentclass[a4paper]{book}
\usepackage[lyric]{songs}

\usepackage[Sonny]{fncychap}

\newindex{titleidx}{cbtitle}

\begin{document}

\showindex{My index}{titleidx}

\begin{songs}{titleidx}

\beginsong{Amazing Grace}[
by={John Newton},
sr={Luke 15:4; 2 Corinthians 4:8,9; Ephesians 2:8; Revelation 14:3},
cr={Public domain.}]

\beginverse
Amazing grace! How sweet the sound
That saved a wretch like me!
I once was lost, but now am found;
Was blind, but now I see.
\endverse

\endsong

\end{songs}

\chapter*{My chapter}

Hello world!

\end{document}


I like to use the fncychap package with the Sonny style, and it works for all my chapters/sections/indices, except for the index generated by the \showindex command. Is there a way to hack this command to make it compatible with the fncychap package?

-
The songs packages uses its own internal formatting for its \songchapter command which is used by \showindex. Adding the following code snippet after loading songs works for me:
\renewcommand{\songchapter}{\chapter*}