\usetypescript[postscript]
\setupbodyfont[postscript,10pt]
\setupinterlinespace[line=20pt]

\def\MyChapter
  {\switchtobodyfont[rm,13pt]%
   \setuplocalinterlinespace[line=30pt]}

\showstruts

\defineinterlinespace[bagger][line=50pt]

% the interline space in MyChapter wins, when not set there, the interline space
% is adapted anyway to the font
%
% \setuphead[chapter][style=\MyChapter,textstyle=,numberstyle=]
%
% the given interlinespace takes precedence
%
% \setuphead[chapter][style=\MyChapter,textstyle=,numberstyle=,interlinespace={line=40pt}]
% \setuphead[chapter][style=\MyChapter,textstyle=,numberstyle=,interlinespace=40pt]

\setuphead[chapter][style=\MyChapter,textstyle=,numberstyle=,interlinespace=bagger]

\starttext

\chapter{Éç\\Éç\\Éç\\Éç}

Éç\par Éç\par Éç\par Éç

\stoptext
