Section header across 2 columns

[David Sumbler]

I'm pretty new to LaTeX.  Writing the introductory pages to a musical
score, I have almost got the layout I want.  But I would like the
headings of the two main sections to be placed centrally above the 2
columns of text below.

The basic structure of my document is this:

%%%%%%%%%%
\documentclass[a4paper,12pt,twocolumn,twoside]{article}

\usepackage{graphicx}
\usepackage{wasysym}
\usepackage{fullpage}

\usepackage{geometry}
\geometry{bindingoffset=0.5cm}

\setlength{\columnsep}{35pt}

\begin{document}
\pagenumbering{roman}
\setcounter{page}{2}

\section*{Introductory Notes}

6 paragraphs of text

\begin{figure*}
  \includegraphics[width=\textwidth]{StagePlan.eps}
\end{figure*}

\section*{Performance Notes}

4 paragraphs of text, followed by several subsections with headings

\end{document}
%%%%%%%%%%

How can I get the 2 main section headings to span both columns?  (The
subsections are fine just as they are.)

David