The whole tone (major second) equals two semitones. It is the most common “step” in melody: most scales are built from an alternation of tones and semitones. In major, the order of steps is tone-tone-semitone-tone-tone-tone-semitone.
On the piano a whole tone spans two keys with one between them (C–D, D–E), while between E–F and B–C there lies only a semitone — and it is this asymmetry that gives the diatonic scale its characteristic “face.” The ear perceives tone and semitone as a large and a small “step”: a passage in whole tones sounds open and confident, whereas the semitone introduces tension. Grasping the difference between tone and semitone is the foundation of ear training and interval construction.
