half step
theoryhaf step
The smallest interval in standard Western music, equal to one semitone.
A half step (called a semitone in British terminology) is the distance between two adjacent keys on a piano — whether from a white key to the nearest black key or from E to F (or B to C, the two pairs of white keys with no black key between them).
Half steps create tension and direction in music. The leading tone (seventh degree of a major scale) is one half step below the tonic and pulls strongly toward it — this gravitational pull is the foundation of tonal music. Chromatic passages (moving by half steps) add colour and intensity.
The two half steps in a major scale (between degrees 3-4 and 7-1) are what give major keys their distinctive bright quality. Change their position and you get a completely different scale.