the labeling of the keys in modern keyboard instruments

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   |   |    |   |   |    |    |   |   |    |   |   |    |    |   |
   | C | D  | E | F | G  | A  | B | C | D  | E | F | G  | A  | B |
   |   |    |   |   |    |    |   |   |    |   |   |    |    |   |
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  • the white keys are labeled with the character set [ABCDEFG]
  • the black keys are labeled by reference to the white keys, using the modifiers 'sharp' (higher frequency than) and 'flat' (lower frequency than)
    • e.g., the key between the C and D key is called either C sharp (C#) or D flat (Db)