How do I change the $\xi$ symbol in mathpazo

Question

I don't like the $\xi$ symbol that mathpazo comes with, so I want to go back to Computer Modern for that symbol alone. How can I do this?

Answer 1

The code is in fontmath.ltx:

\DeclareMathSymbol{\xi}{\mathord}{letters}{"18}

To make the change you want, you can fetch the CM definition of letters and change it into

\DeclareSymbolFont{CMletters}{OML}{cmm}{m}{it}

and then

\DeclareMathSymbol{\xi}{\mathord}{CMletters}{"18}