Related Clues:

• Musical scale unit
• See 11 Across
• 'Note to self' note
• Exec's reminder
• Staff character
• Message passed in class
• Office heads-up
• In-tray delivery
• Score component
• Little letter
• "Half," "quarter" or "eighth" follower
• It can go flat
• Eff or Gee
• A through G, but not H
• It might have the heading 'Re:'