Your code is operating in the Voice context, and you need to be in the
Staff context:
\set Staff.fontSize = #new-size
\override Staff.StaffSymbol.staff-space = #(magstep new-size)
\override Staff.StaffSymbol.thickness = #(magstep new-size)
By the way, I wouldn't reduce the thickness property like
Hi Orm,
2014-06-19 18:59 GMT+02:00 Orm Finnendahl :
> is there a way to reduce the global staff size of all staffs in an
> orchestral score for selected pages (or a selected region) on the fly
>
No easy way.
See also http://lsr.di.unimi.it/LSR/Item?id=862 (just in case...)
> I'm on 2.9.15.
>
