SECOND. The smallest interval in the scale used for musical purposes. It is described by notes which are next to each other on the stave, or by letters which lie next each other in the alphabet, as A B, B C, C D♯, E♭ F♯.
Three kinds can be practically distinguished. The minor second, which is equal to a semitone, as at (
b) in the example; the major second, which is equal to a tone, as at (
a); and the augmented second, which is equal to three semitones, as at (
c). They are all discords, but are characterised by different degrees of roughness. The minor second is extremely harsh, the major decidedly so, though not so extremely, and the augmented second but slightly. In ordinary musical usage the last is actually the same interval as a minor third, which is not looked upon as a dissonance at all; nevertheless the ear, distinguishing relations instinctively, classifies the combinations according to their context as having a dissonant or consonant significance. Thus when the context suggests the interval A♭ B♮, the mind will not accept it as final, but as a dissonance requiring resolution; whereas if the same interval could be expressed as A♭ C♭, it might be recognised as a characteristic portion of the minor chord of A♭, and could be accepted as final without desire for further motion.—The numerical ratios of the several intervals in just intonation are given as follows:—the minor second, 16:15; the grave major second, 10:9; the acute major second 9:8; and the augmented second 75:64.
