A semitone, or half-step is a musical interval. It is the smallest interval commonly used in Western music, and is considered the most dissonant. The most commonly written form of this interval is the minor second, notated using two adjacent letter names (for example C and D♭), but the augmented unison is also used, both notes having the same letter-name, with one of the notes being inflected by an accidental (for example C and C♯). In twelve-tone equal temperament all semitones… (More on Semitone)