A semitone is the smallest interval in the standard Western tuning system. It is the distance between two adjacent keys on the piano, whether white to black or white to white when no black key intervenes.

Twelve semitones make up an octave. Scales and chords are built from specific patterns of semitones and whole tones. The semitone produces a strong sense of tension or leading when used as a half-step resolution, as in the leading tone that rises to the tonic.

Singers and instrumentalists must produce semitones accurately for correct intonation. In equal temperament every semitone is the same size; other tuning systems may vary the exact ratios. Understanding semitones is basic to reading accidentals, constructing scales, and analyzing harmony.

• Smallest interval in Western music
• Distance between adjacent piano keys
• Twelve semitones equal one octave
• Creates tension and resolution in melody and harmony