# Compatibility of musixtex with amsmath

I've been using musixtex and amsmath in the same document (article class) up until I today encountered the problem that whenever I type \cup for a set union, a quaver appears instead (or sometimes compiling just reports an error). I am not within the environment called by \begin{music} when this occurs. Is there anything I can do to fix this?

To give an example:

\documentclass[11pt,a4paper]{article}
\usepackage{amsmath} %Maths stuff
\usepackage{amsthm} %Theorems
\usepackage{amsfonts}  % for blackboard bold, etc
\usepackage{musixtex}

\begin{document}
$A\cup B$
\end{document}

• welcome to tex.xs. please provide a small example that will compile and show the problem, so that others can experiment. – barbara beeton Dec 3 '15 at 20:00
• Oh - sorry, I've added an example now. – Lammey Dec 3 '15 at 20:08

musixtex overrides the latex \cup command, but you could do the following to use one or other definition, depending on whether you are in math.

\documentclass[11pt,a4paper]{article}
\usepackage{amsmath} %Maths stuff
\usepackage{amsthm} %Theorems
\usepackage{amsfonts}  % for blackboard bold, etc
\let\cupA\cup
\usepackage{musixtex}
\let\cupB\cup

\protected\def\cup{\ifmmode\expandafter\cupA\else\expandafter\cupB\fi}

\begin{document}

1: $A\cup B$

2: A \cup B

\end{document}

• That's fantastic, thankyou! – Lammey Dec 3 '15 at 20:34
• actually, \cup for math isn't defined by amsmath -- it's a symbol name command carried over from plain tex. anyhow, this is a good approach when such symbol names are re-used and their context can be separated by whether it's within math or not. – barbara beeton Dec 3 '15 at 20:42