Sharps, flats and half steps

Half steps and whole steps

Play any key, then the very next key to its right, black or white, with nothing in between. That distance is a half step, also called a semitone, and it is the smallest step on the piano. Most half steps go from a white key to a black key or back: from C to the black key just above it, then from that black key to D. In two places in every octave, though, two white keys touch with no black key between them, so the half step goes from white to white: E to F and B to C.

Two half steps make a whole step, or tone. C to D is a whole step, with the black key between them as the halfway point. E to F is only a half step, so a whole step up from E lands on the black key just right of F.

Sharp, flat and natural

A sharp (♯) raises a note by a half step: C♯ is the key just right of C, F♯ the key just right of F. A flat (♭) lowers a note by a half step: B♭ is the key just left of B, E♭ the key just left of E. In plain text the signs are often typed as a hash and a small b, as in C# and Bb.

The natural sign (♮) cancels a sharp or a flat and takes the note back to its plain letter name, a white key. You meet it when a sharp or flat would otherwise still apply, as the staff section below shows.

One black key, two names

Look at the black key between C and D. Counted up from C, it is C♯. Counted down from D, it is D♭. Both names are right, because it is one key with one sound, and the same goes for all five black keys of the octave:

• C♯ or D♭, between C and D
• D♯ or E♭, between D and E
• F♯ or G♭, between F and G
• G♯ or A♭, between G and A
• A♯ or B♭, between A and B

Two names for the same key are called enharmonic equivalents. On the piano they are the same key and the same sound. On paper, the name depends on the key of the piece, which is why one song writes F♯ and another G♭ for the very same black key.

The gaps in the black keys lead to a curiosity. Since E to F is already a half step, E♯ is played on the F key, and since B to C is one too, C♭ is played on the B key. These spellings are rare and only turn up in keys with many sharps or flats, so you can leave them for later.

Sharps and flats on the staff

On the staff the sign comes just before the note, on the same line or space as the note head, so you read it first. Written inside the music like this, sharps, flats and naturals are called accidentals.

An accidental lasts until the end of the bar. Every later note on the same line or space in that bar keeps it, even without a sign of its own. The next bar line cancels it, and a natural sign cancels it sooner.

You can watch a natural at work in the first full bar of Für Elise: E, D♯, E, B, then D with a natural sign, because without it the D♯ from earlier in the bar would still apply.

Sharps and flats can also be set once for a whole piece, as a key signature: a group of signs right after the clef, at the start of every line. Key signatures come back in the lesson on the major scale.

Practise: find the sharp or flat

The exercise below asks for black keys by one name or the other, in any octave, with Labels set to Off. Read the letter first, find that white key, then take one step: to the right for a sharp, to the left for a flat. For E♭, think “just left of E”, not “just right of D”. Reading each name the way it is written is the habit that makes sheet music easier later.

Each note you play appears on the staff, written as a sharp, so E♭ shows up as D♯: the same key under its other name. If you set Labels to C D E, the black keys show their sharp names only, so trust the step rather than the label. Move on when you can find all ten without a miss.