Half steps, whole steps, and the in-between notes

So far we’ve talked about seven notes per octave — A La through G Sol . But if you look at a piano keyboard, you’ll count more keys than that inside one octave.

Twelve keys, not seven. Five of them are black, sitting between certain pairs of white keys. Those black keys are the in-between notes — the ones that don’t have their own letter.

The smallest step

The distance from any key to its immediate neighbor — black or white — is called a half step (or semitone). It’s the smallest distance Western music normally measures.

Two half steps stacked together make a whole step (or whole tone). That’s it. Every interval, every scale, every chord in this entire site is built from these two units.

1 half step = 1 semitone · 2 half steps = 1 whole step

Where the black keys fit

Look at the keyboard again. The black keys appear in groups of two and three, with two “gaps” each octave — between E Mi and F Fa , and between B Si and C Do .

That’s the asymmetry beginners trip over. The pattern from one white key to the next is:

whole — whole — half — whole — whole — whole — half

Starting on C Do and going up: C Do to D Re is a whole step, D Re to E Mi is a whole step, E Mi to F Fa is a half step (no black key between them), F Fa to G Sol is a whole step, and so on.

Sharps and flats

The black keys need names. They get them in relation to the white keys they sit between.

A note one half step above a letter is that letter sharp (♯). A note one half step below a letter is that letter flat (♭).

So the black key between C Do and D Re can be called:

• C# Do# (“C sharp”) — one half step above C Do , or
• D♭ (“D flat”) — one half step below D Re .

It’s the same key, the same pitch — just two ways to name it. Which name you use depends on context (we’ll see why in Part II when we talk about key signatures).

The 12 notes

Put it all together: there are 12 distinct notes per octave, alternating white and black on a piano. Going up from C Do :

C Do — C# Do# — D Re — D# Re# — E Mi — F Fa — F# Fa# — G Sol — G# Sol# — A La — A# La# — B Si — (and back to C Do )

These twelve notes, repeated octave after octave across the whole range of hearing, are the raw material of all Western music — and of the fretboard-tempered Greek music played on bouzouki.

Recap

• A half step is the distance from any key to its nearest neighbor — the smallest unit Western music uses.
• A whole step is two half steps.
• Sharps raise a note by a half step; flats lower it by a half step.
• Between E Mi / F Fa and B Si / C Do there is no in-between black key — those pairs are already a half step apart.
• An octave contains 12 distinct notes in total.