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Semitone – Definition
A semitone is the smallest interval used in the standard Western system of music. On the piano, it is the distance from one key to the nearest adjacent key, whether that key is black or white. In American English, a semitone is also commonly called a half step.
What is a Semitone?
The semitone is the fundamental building block of scales, chords, and melodies. Two semitones make a whole tone (whole step), and an octave consists of twelve semitones in the chromatic scale.
On the piano, examples of semitone intervals include C to C♯, E to F, B to C, and F♯ to G. Every adjacent pair of keys represents one semitone.
How is a Semitone used in piano playing?
Understanding semitones is essential for building scales and chords correctly. For example, changing a major chord into a minominor chord requires lowering the third by one semitone.
Semitones also play an important role in melody and harmony. They create tension and resolution, particularly in leading tones that naturally resolve to the tonic.