Diatonic and chromatic half steps · Accidentals · Music theory
A half step can be written in two ways. If the two notes have different names, like C–D♭ or E–F, it is diatonic; if they have the same name, like C–C♯, it…
Diatonic and chromatic half steps
A half step can be written in two ways. If the two notes have different names, like C–D♭ or E–F, it is diatonic; if they have the same name, like C–C♯, it is chromatic. They sound the same, but they are written and used differently.
Why the distinction is useful
The distinction explains how notes behave. A diatonic half step joins two different scale degrees, and tends to feel like a step with a direction: B–C. A chromatic one alters the same degree and colors the note without changing degree: F–F♯.
That is why spelling depends on where the music goes: what rises is written with sharps and what falls, with flats. C–C♯–D and D–D♭–C use the same keys and the same melodic logic.