Enharmonic notes

Two notes are enharmonic when they sound the same but are written differently. F♯ and G♭ are one key on a piano and two different notes on a page.

The obvious question is why anyone bothers. The answer is that notation is not a picture of the keyboard — it is a description of musical function, and the letter carries meaning the pitch alone does not.

The rule that decides it

A scale uses each letter name exactly once. That single rule settles almost every spelling question.

Take the D major scale. Its notes are D, E, F♯, G, A, B, C♯. Suppose you wrote G♭ instead of F♯:

• D E F♯ G A B C♯ — seven letters, each used once. Readable.
• D E G♭ G A B C♯ — G appears twice, F not at all. The scale would look like it skips a step and then repeats one.

On a stave the second version is genuinely harder to read: two notes on the same line or space where the pattern expects consecutive positions.

The surprising ones

Two pairs catch people out, because there is no black key involved:

• E♯ is F. F♭ is E.
• B♯ is C. C♭ is B.

These are not tricks. C♯ major genuinely contains E♯ and B♯, because the scale needs a version of every letter. Writing F and C instead would use F twice and skip E entirely.

They also appear in ordinary keys as passing accidentals — an E♯ in a piece in F♯ major is a raised fourth degree, and calling it F would hide what it is doing.

Double sharps and double flats

Occasionally a note needs raising or lowering by two semitones: F𝄪 sounds like G, B𝄫 sounds like A. They exist for the same reason — keeping one letter per scale degree.

You meet them most often in harmonic minor in sharp keys. G♯ harmonic minor raises its seventh degree from F♯ to F𝄪, because the seventh degree has to be some kind of F.

When it genuinely does not matter

For a single note played in isolation, with no key context, the spelling carries no information — a lone black key between F and G is whatever you want to call it. Guitarists and producers often default to sharps for that reason.

The moment the note sits inside a key or a chord, though, the spelling is telling you what the note is doing, and getting it wrong makes the music harder to read.