Enharmonic Key Signatures

Help With Enharmonic Notes and Key Signatures:

• Easy-to-Read Breakdown of the 15 Key Signatures


• Outline of Musical Keys by Keynote


• Get to Know the Diatonic Scale

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. 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:

• 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; which really means it’s just one scale going by two different names (see picture #1).

Notes and chords can 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).

The Point of Enharmonic Key Signatures

Why bother keeping around two key signatures if their scales are the same? 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 Sharps	Enharmonic Key:	No. of Flats
B major / G# minor	5	Cb major / Ab minor	7
F# major / D# minor	6	Gb major / Eb minor	6
C# major / A# minor	7	Db major / Bb minor	5

• Continue Reading: What Are the Forgotten Key Signatures?