Second (interval)

Two seconds

The minor second is the smallest step of the diatonic scale, a semitone. It creates strong friction between the two notes: they lie so close together that the ear hears them as charged and pressing. Its most important job in tonal music is that of the leading tone: the seventh degree of a major scale lies a semitone below the root and audibly pulls towards it.

The major second is the whole tone. It sounds mildly dissonant: clearly tenser than a third or fifth, but not as full of friction as the minor second. It is mobile and flowing and counts as the backbone of every melody.

Seconds in the scale

The major scale consists of five whole tones and two semitones (whole, whole, half, whole, whole, whole, half). Two whole tones in a row make a major third. If both whole tones are tuned pure (9:8), this third (81:64) is larger than the just third 5:4 by a syntonic comma of about 21.5 cents; in equal temperament the difference is about 14 cents.

A second between the sixth and seventh degree of harmonic minor has the peculiarity of measuring a tone and a half: the augmented second.

On the guitar

A minor second corresponds to one fret apart, a major second to two frets. If you fret the high E string (329.63 Hz) at the 1st fret, F sounds; at the 2nd fret, F♯. The fret frequencies follow equal temperament and deviate minimally from the just ratios.

Common mistakes

• Equating second with semitone: There is a minor second (semitone) and a major second (whole tone).
• Counting: The second is called that because it spans two degrees, not two semitones.
• Leading the leading tone downwards: The minor second below the root pulls upwards.