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Why are there only five black piano keys per octave?

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Black piano key layout.

It looks like some white keys are missing an accidental.

Image © Brandy Kraemer
Question: Why are there only five black piano keys per octave?
Don’t all piano notes have sharps and flats?

Answer: They do. Every note can have a sharp or flat – which is what a black piano key is – but there are fewer black piano keys than white ones.

Look at image #1: The C-note appears to have no flat, because there is no black key directly to its left. But C does have a flat, it’s just disguised as B. Here’s why:


The musical scale on which the piano keyboard is based is called the diatonic scale. This scale has intervals of whole steps and half steps in a specific pattern. The pattern of the C major scale is as follows:

C –whole- D –whole- Ehalf- F –whole- G –whole- A –whole- Bhalf- C


As you can see, there are two half step intervals in a major scale. In C major, they fall between B-C, and E-F (see image #2). Since there is already a half step between these notes, adding a black key – which lowers a note by a half step – would be unnecessary.

Tip: The B note (along with B chords and key signatures) can also be written as C flat … its name simply depends on the key one is using. These notes are examples of enharmony.


Continue This Lesson:

Back to Beginner Lesson Index    | ► Locate the Middle C Key on the Piano
Layout of the White Piano Keys   | ► Notes of the Piano

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