Problem changing time signiture

I have a piece for four instruments. I am trying to add a measure at the start in a different time signature from the rest of the piece. However, each time I try to change the time signature at the start, it only changes for two of the instruments. So I have two questions:

  1. What’s going on here with not being able to change the time signature?

  2. Is there a way to insert a measure of a specified time signature?

Here’s the first page. I’d like to append a 12/8 measure to the front:


It looks like you’ve used local time signatures. These apply to individual staves rather than the whole lot. It’s probzbly easiest to delete all of the time signatures at the start, then add a new time signature the regular way.

And yes, of course. Having made a new global time signature at the start, select that time signature and type Shift+B 1 Enter. Then add a new time signature at bar 2. Then change your bar 1 time signature to 12/8. If a bar is added in between your old bar 1 and your old bar 2, use the System Track to delete it (or select the barline and type Shift+B -1 Enter).