\documentclass[a5paper,12pt]{scrartcl}
\usepackage{fontspec}
%% --------------------------------------------------------------------
%% weirdness ahead
%% --------------------------------------------------------------------
\setmainfont
  [Numbers=Lining,
   BoldFont={TeX Gyre Pagella Bold},
   BoldItalicFont={TeX Gyre Termes BoldItalic}]
  {EB Garamond}
%% --------------------------------------------------------------------

%% --------------------------------------------------------------------
%% excerpt from samples/knuth.tex
%% --------------------------------------------------------------------
\def\knuth{%
  Thus, I came to the conclusion that the designer of a new
  system must not only be the implementer and first
  large--scale user; the designer should also write the first
  user manual.

  The separation of any of these four components would have
  hurt \TeX\ significantly. If I had not participated fully in
  all these activities, literally hundreds of improvements
  would never have been made, because I would never have
  thought of them or perceived why they were important.

}

%% --------------------------------------------------------------------
%% main
%% --------------------------------------------------------------------
\begin{document}

  \section{regular}     {\rmfamily\upshape\knuth}
  \section{bold face}   {\rmfamily\bfseries\knuth}
  \section{italic}      {\rmfamily\itshape\knuth}
  \section{slanted}     {\rmfamily\slshape\knuth}
  \section{bold italic} {\rmfamily\bfseries\itshape\knuth}

\end{document}