Apple Logic Pro 9 - Manual (Page 947)

If you make a cut in the middle of a bar—in a section where the time signature doesn’t
change—two corresponding shorter measures are inserted, with the original time signature
resuming after the cut.
Likewise, it is also possible to merge two subsequent measures into one longer measure,
by using the Glue tool in the Signature track.
Deleting Signatures
You can delete all signatures in a project, except the initial time and key signature.
To delete a signature
Do one of the following:
µ
Select the signature in the Score Editor, Signature List, or Signature track, then choose
Edit > Delete (or press Delete).
Tip: To erase all time signature events, choose Edit > Select Similar Objects after selecting
a signature, then press Delete.
µ
Click the signature with the Eraser tool in the Score Editor, Signature List, or Signature
track.
Creating and Choosing Signature Alternatives
Signature alternatives are just that: alternative versions of all signatures in the Signature
List or Signature track.
To create signature alternatives
Do one of the following:
µ
Choose Options > Signature Alternatives in the Signature List, then choose a Signature
List.
947 Chapter 31 Working with Notation