MIDI : Score Editor : Key Changes

Key Changes
You can add, edit, and delete Key Signatures in your score. Key Signatures affect the note spelling of MIDI notes in the score. For example, MIDI note number 58 (“B-flat 3”) is B-flat in F major, but it is A-sharp in B major.
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You can also add and delete Key Signatures in the Key Signatures ruler in the Edit window or in any MIDI Editor window.
To add a Key Signature:
1 With the Note Selector, Grabber, or Pencil tool, Right-click at the location in the score where you want to change key and select Insert > Key Change.
2 In the Key Change dialog, select the mode (major or minor), the key, its location and range, and how you want it to affect pitched tracks.
3 Click OK.
The selected Key Signature is displayed in the score and the note spellings for notes after the key change are updated accordingly.
To edit a Key Signature:
1 With the Grabber tool, double-click the Key Signature you want to edit.
2 Enter values in the Key Change dialog and click OK.
To delete a Key Signature:
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With the Grabber tool, Alt-click (Windows) or Option-click (Mac) the Key Signature you want to delete.