Switch polyrhythms in staffs

[Hajo Dezelski]

Hello,

there is one problem which I can not resolve:

On a Pianostaff I have an "upper" voice with \time 18/16 which I coded:
\score ...
 \new Staff = "upper" { 
          ...

        \time 3/4 
        \set Staff.timeSignatureFraction = #'(18 . 16)
        \compressMusic #'(4 . 6)
        \soprano  }

and  a lower staff:
        \new Staff = "lower"  { ...  \time 3/4 \bass }

...
}

This
works fine until I have to switch the measure to 3/4 in the upper and
18/16 in the lower staff. And I have to do that a lot of times.

Where and how can I perform these changes.

Thanks in advance for your advice.

  All the best  Hajo

-- 
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... indessen wandelt harmlos droben das Gestirn