Enharmonic Key Signatures

Learn Why Some Notes and Scales Go By Two (Or More) Names

Enharmonic scale equivalents.
(Click to enlarge) The scales of C# major and Db major . Sidney Llyn

What Are Enharmonic Key Signatures?

If you’re familiar with the circle of fifths – or you just know your way around the key signatures – you may have noticed a few anomalies. For example, some keys, like B-sharp and F-flat major, are seemingly absent while others go by two names: If you compare the notes of both C-sharp major and D-flat major, you’ll realize that they are exactly the same. Observe:

  • C-sharp major: C#   D#    E#    F#   G#   A#   B#
  • D-flat major:     Db   Eb     F     Gb   Ab   Bb    C

 

Likewise, their respective relative minors are also identical in tone:

  • A-sharp minor: A#    B#   C#    D#    E#    F#    G#
  • B-flat minor:     Bb    C     Db    Eb     F     Gb    Ab

 

When scales are identical in this way, they’re known as enharmonic equivalents. This means that these scales are really just one scale going by two different names (see image).

Notes and chords also have enharmonic equivalents; and technically (but not practically), each can go by an infinite amount of names: E quadruple-flat could be another way of saying C (see picture #2). In practice, however, notes and scales rarely go by more than two names, and there are only six key signatures with enharmonic equivalents (see table, below).

 

What Is the Point of Enharmonic Key Signatures?

So, why bother keeping around two key signatures if their scales are the same anyway?

Because it gives you the option of writing a scale using either sharps or flats; and, since it's best to use only one type of accidental in a composition, this option makes certain key changes easier to compose and read.


For example, if you switch from the key of F# major to its fifth, C# major (which contain 6 and 7 sharps, respectively), it would be silly to confuse your eyes and opt for the 5-flatted Db major instead.

There are, however, exceptions to this advice, especially when exploring modal scales.
 

The Enharmonic Key Signatures Are:

Major / Relative Minor:No. of SharpsEnharmonic Key:No. of Flats
 
B major / G# minor5Cb major / Ab minor7
F# major / D# minor6Gb major / Eb minor6
C# major / A# minor7Db major / Bb minor5

 

Related Reading:

  • What Are the Forgotten Key Signatures?
    The circle of fifths shows only the working scales. But, if we expand on its pattern, we can see that it’s actually more of an infinite spiral, so there’s no end to the possibilities of musical scales. One could write a song in the key of B quadruple-flat; learn more.
  • Easy-to-Read Breakdown of the 15 Key Signatures
    Most notes of the staff name both major and minor key signatures, but some are only seen as one or the other. A few keynotes don't name any working key signature, and their scales are considered rare or theoretical. Consult this table to learn more, and to strengthen your understanding of the diatonic scale.
  • All About Key Signatures
    Everything you need to know about the accidentals & key signatures.

  • Use the interactive key signature locator to identify or double-check your key.

  • There are always two keys that relate to one another more than any other key. Find out what this means.
  • The Diatonic Scale: Comparing Major & Minor
    Major and minor are often described in terms of feelings or mood. The ear tends to perceive major and minor as having contrasting personalities; a contrast that is most obvious when the two are played back to back. Learn more about major and minor scales and keys.

 

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