Notes and intervals
Enharmonic equivalent
Enharmonic equivalents are two different names for the same pitch, like F# and G♭: on the guitar they are the same fret, but the correct name depends on the key and the chord.
What are enharmonic equivalents?
Two notes are enharmonic when they sound the same but are spelled differently. The 2nd fret of the 6th string is F# or G♭; the 1st fret of the 5th string is A# or B♭. The common pairs: C#/D♭, D#/E♭, F#/G♭, G#/A♭, A#/B♭.
Natural notes have equivalents too: E = F♭, F = E#, B = C♭, C = B#. It all comes from sharps and flats: raising F by a semitone or lowering G by a semitone lands on the same fret. On the guitar the sound is identical; only the spelling changes.
Why does the correct name matter?
Because chords are built in thirds, skipping every other letter. A major is spelled A, C#, E (letters A, C, E), not A, D♭, E: D♭ would suggest a diminished fourth. A♭ major is A♭, C, E♭, not G#, C, D#.
Correct spelling tells you at a glance which interval you are playing. In G7 (G, B, D, F) and D♭7 (D♭, F, A♭, C♭), B and C♭ are the same fret: that is why both chords share the same tritone, the basis of tritone substitution.
Enharmonic keys
At the bottom of the circle of fifths, three keys have two possible names, each with its own key signature:
| Sharp key | Flat key |
|---|---|
| B major (5 sharps) | C♭ major (7 flats) |
| F# major (6 sharps) | G♭ major (6 flats) |
| C# major (7 sharps) | D♭ major (5 flats) |
Musicians usually pick the simpler signature: D♭ rather than C#, B rather than C♭. The interactive circle of fifths shows these pairs side by side.
Exercise: one barre chord, two names
Play the E-shape barre chord at the 4th fret (root on the 6th string, 4th fret). Depending on the song, it takes a different name:
- In an E♭ major progression (E♭, A♭, B♭), it is A♭, the IV chord.
- Barre the Em shape in the same spot, in an E major progression (E, G#m, A, B), and it is G#m, the iii chord.
Same bass note, same fret, but the right name makes the chart readable. Diminished seventh chords take this further: Gdim7 (G, B♭, D♭, F♭) contains the same pitches as B♭dim7, C#dim7 and Edim7. One shape, moved up three frets at a time, covers all four.
Key takeaways
- Enharmonic = same sound, two names (F# and G♭).
- The correct name depends on the key: each letter once per scale.
- Chords are spelled every other letter: A, C#, E, not A, D♭, E.
- B/C♭, F#/G♭ and C#/D♭ major are enharmonic keys.
Frequently asked questions
Do F# and G♭ sound exactly the same?
On a guitar or piano, yes: equal temperament splits the octave into twelve identical semitones. A violinist or singer, however, may pitch them very slightly differently depending on the harmony.
Why not write everything with sharps?
Because it would make music harder to read. In F major, writing A# instead of B♭ would give two A's and no B in the scale, and the B♭ chord (B♭, D, F) would become A#, D, F, which no longer looks like a stack of thirds.
How do I know whether to write G# or A♭?
Look at the key and what the note is doing. In E major (four sharps), it is G#, the third of E. In E♭ major (three flats), it is A♭, the fourth degree. When in doubt, go back to the rule: one letter per degree.
Related terms
Practise in the workshop
Take it from theory to the fretboard
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