\starttypescript[bitter]
        \definefontsynonym[Bitter-Regular]
        [file:Bitter-Regular]
        \definefontsynonym[Bitter-Italic]
        [file:Bitter-Italic]
        \definefontsynonym[Bitter-Bold]
        [file:Bitter-Bold]
        \definefontsynonym[Bitter-BoldItalic]
        [file:Bitter-BoldItalic]
\stoptypescript

\starttypescript[bitter]
        \setups[font:fallback:serif]
        \definefontsynonym[Serif]       [Bitter-Regular]
        [features=default]
        \definefontsynonym[SerifItalic]       [Bitter-Italic]
        [features=default]
        \definefontsynonym[SerifBold]       [Bitter-Bold]
        [features=default]
        \definefontsynonym[SerifBoldItalic]       [Bitter-BoldItalic]
        [features=default]
\stoptypescript

\starttypescript[bitter]
        \definetypeface[bitter] [rm] [serif] [bitter] [default]

\stoptypescript