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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\usemodule[streams]
\def\StartCouple{\page\SwitchToNormal}
\def\StopCouple {\SwitchToNormal \SynchronizeLeftAndRight
\FlushLeftAndRight}
\def\Original {\SwitchToNormal\SynchronizeLeftAndRight\SwitchToLeft}
\def\Translation{\SwitchToRight}
%%So you put the part of your document where synchronization should
%%take place between \StartCouple and \StopCouple. After that ,
%%\Original and \Translation switches between even and odd pages.
\starttext
\scale[width=\textwidth,height=\textheight,factor=fit]{\ss m-streams}
\page
\StartCouple
\Original
this is an original text \crlf
\input knuth
\blank[1cm]
\Translation
THIS IS THE TRANSLATION \crlf
\input tufte
\Original
\ss this is an original text \crlf
\input knuth
\Translation
\tt THIS IS THE TRANSLATION \crlf
\input tufte
\StopCouple
\stoptext