Polytonic Greek without changing other fonts

Question

I would like to use the hitec class for a handout, I really like the look of it. However, I'd like to include some polytonic Greek as well. I'm not sure how to enable the use of a suitable font without all the roman or italic fonts changing too ... Basically that is to say, I would like the document to appear with the same fonts for the non-Greek parts as is the default, but the Greek part in a font such as Cardo, which gives beautiful Greek characters. (Example below, using the cludge of setting the mono font to Cardo which I thought might work... uncommenting the commented parts should show the font-changes which I do not want).

\documentclass[a4paper]{hitec}
\author{\textit{Ms Author}}
\date{September 9, 1999}
\title{A fancy title}

%\usepackage{fontspec} 
%\setmonofont{Cardo}

\begin{document}

\maketitle

\section{Test}

This is a test
%\texttt{ἄειδε θεὰ Πηληϊάδεω Ἀχιλῆος}

\end{document}

Answer 1

Don't abuse the mono font, use polyglossia and its interface:

\documentclass[a4paper]{hitec}
\author{\textit{Ms Author}}
\date{September 9, 1999}
\title{A fancy title}

\usepackage{fontspec}
\usepackage{polyglossia}

\usepackage{lipsum}

\setmainlanguage{english}
\setotherlanguage[variant=polytonic]{greek}


\newfontfamily\greekfont{Cardo}

\begin{document}

\maketitle

\section{Test}

\lipsum[1-2]

\textgreek{ἄειδε θεὰ Πηληϊάδεω Ἀχιλῆος}

\end{document}

A magnified version