> Thomas Fehige <mailto:thomas@fehige.de>
> 8. Juni 2016 um 10:35
> Nevertheless, I prefer to keep all the font and fontsize definitions 
> and tweaks together in the preamble. This poster is not the only work 
> I'm planning to do in ConTeXt, and I need to learn to swim while 
> already in the water ;) .
For short texts where you want a certain style and size (e.g. a title 
page or a poster with few words) \definedfont is the recommended method, 
for larger amounts of the text (e.g. the abstract of a book) you can use 
\switchtobodyfont to change the size.
> Meanwhile I found the command \definebodyfontswitch and defined 
> switches like \normalsize, \scriptsize, \large, \Large etc.
The \definebodyfontswitch creates only a command which uses 
\switchtobodyfont with a fixed number of arguments.
> But this doesn't explain why \definebodyfontenvironment did not do 
> anything in my MNWE. The fonts book is not very clear on its intended 
> use.
You put spaces before and after = which aren’t allowed there.

\definebodyfontenvironment
   [24pt]
   [         small=22pt,
               big=28pt,
                 x=22pt,
                xx=16pt,
                 a=30pt,
                 b=40pt,
                 c=50pt,
                 d=60pt,
    interlinespace=30pt,
                em=italic]

\setupbodyfont[palatino,24pt]

\starttext

\startlines
  \tf   tf
{\tfa  tfa}
{\tfb  tfb}
{\tfc  tfc}
{\tfd  tfd}
{\tfx  tfx}
{\tfxx tfxx}
\stoplines

\stoptext

Wolfgang