Major second
Two semitones, the whole-tone step of the scale.
What it means
The major second comprises two semitones and corresponds to the whole-tone step. It is the most common step interval of the diatonic scale — five of its seven steps are major seconds. As a sonority it counts as dissonant, as a melodic step, by contrast, as self-evident and inconspicuous.
Musical use
Melodically the major second is the normal case of stepwise motion. It connects notes without forcing a direction — in this it differs from the minor second, which pulls as a leading-tone step. Where a whole tone stands instead of an expected semitone, this noticeably changes the character of a key: the Mixolydian seventh degree lies a whole tone below the root, and the cadence thereby loses its goal.
As a sonority the major second is rich in tension. It appears as a suspension that resolves downward into the third, as a component of the second-inversion chord (four-two), and as a building block of clusters. In inversion it becomes the minor seventh — the numbers of the two intervals add up to nine, and major becomes minor.
For intonation it is to be noted that the whole tone is not everywhere the same size: in just tuning there are two whole tones of different width, whose difference is the syntonic comma. On tempered instruments this difference falls away; in free ensemble playing it remains audible.
In just tuning the major whole tone has the ratio 9:8. As a sonority it counts as a dissonance that is resolved in traditional study of composition; in clusters, in jazz, and in the music of the twentieth century it is often used as a colour. Inverted it yields the minor seventh. In just tuning the major and minor whole tones differ, in the tempered system both are the same size.
Performance practice
Sing the major second wide enough — it is often taken too narrow, especially upward. To memorize it, use the beginning of familiar melodies that begin with a whole-tone step. And distinguish distinctly between whole-tone and semitone steps while playing; whoever treats both alike blurs the character of the key.