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