columns.tex

\usepackage{environ}
\usepackage{multicol}

\newsavebox{\songbox}

\NewEnviron{song}{% can also have arguments
    % \clearpage
    % Add song title, at as argument etc.
    %
    % The content is \BODY
    % Let's save it in normal single column mode:
    \savebox{\songbox}{%
    \begin{minipage}{\linewidth}%
        \BODY
    \end{minipage}%
    }%
    % To high? (Replace \textheight if required)
    % \ht = hight, \dp = depth, both together is the total height
    \ifnum\dimexpr\ht\songbox+\dp\songbox > \textheight
        % Typeset again in two column mode:
        \begin{multicols*}{2}%
           \BODY
        \end{multicols*}%
    \else
        % Size is already OK, so use the content of the saved box:
        \usebox{\songbox}%
    \fi
}