The following code:

\enabletrackers[context.trace]

%\usemodule[article-basic]

\starttypescript [sans] [optima]
   \setups[font:fallback:sans]
   \definefontsynonym [Sans]           [file:Optima.ttc(Optima Regular)]     [features=default]
   \definefontsynonym [SansBold]       [file:Optima.ttc(Optima Bold)]        [features=default]
   \definefontsynonym [SansItalic]     [file:Optima.ttc(Optima Italic)]      [features=default]
   \definefontsynonym [SansBoldItalic] [file:Optima.ttc(Optima Bold Italic)] [features=default]
\stoptypescript

\definetypeface [optima] [ss] [sans] [optima] [default]

\setupbodyfont [optima]

\starttext

\startMPpage[instance=doublefun]
  picture pic;
pic := textext("\definebodyfont[14.9pt][rm][default=Regular at 14.9pt]\switchtobodyfont[14.9pt]\setupinterlinespace[16.9pt]\framed[align=center,frame=off,offset=none,width=335.350bp]{\colored[r=0.000, g=0.000, b=0.000]{\rm (Artifact)\\}}");
draw pic scaled 1.13;
\stopMPpage

\stoptext

Produces nice Optima at 14.9pt without \usemodule[article-basic] (as above), but with \usemodule[article-basic] included, the output becomes some serif (modern?) font, but only if I use nonstandard font sizes.

Took me some time to hunt this one down.

I actually don’t know what article-basic does for me (I started out with an example given to me by Hans) and I don’t need it now, but I might need it later in combination with my own stuff

G