Wolfgang,

I did it before sending the message and it didn’t work.

\startbuffer[buffer:inside]
\definebodyfont[17pt]
\definefontfamily[mainface][rm][TeX Gyre Pagella]
\setupbodyfont[mainface, 17pt]
\starttext
\input zapf
\stoptext
\stopbuffer
\starttext
\typesetbuffer[buffer:inside]
\stoptext

Neither does it work now.