\documentclass{article}
\usepackage{graphicx}
\usepackage{alltt}

\title{<%= song.title %>}
\date{}

\begin{document}

\maketitle

\begin{alltt} \rmfamily
<%= song.lyrics %>
\end{alltt}

<%- p "tmp sheet file: #{tmp(song_sheet_pdf song.id)}" -%>
<%- if File.file? tmp(song_sheet_pdf song.id) -%>
\begin{figure}
  \centering
  \includegraphics[width=\textwidth]{<%= tmp(song_sheet_pdf song.id) %>}
\end{figure}
<%- end -%>

\end{document}