If you have a split system with two staves you can set different keys for the upper and lower staff.
Procedure
- Click in the system to make one of its staves the active staff.
- Open the Score Settings dialog on the Staff page.
- Set a key for the upper staff.
This automatically sets the lower staff to the same key.
- If you need to set a different key for the lower staff, activate the “Lower Staff” checkbox and set a key for this.