Second (interval)
The interval of a second.
What it means
The second is the interval between neighbouring scale degrees — the step from one note to the next. It appears in three forms: the minor second with one semitone, the major with two, the augmented with three. As a combined sound it counts throughout as dissonant; as a melodic step it is the normal case.
Musical use
Melodically, second-wise movement carries the coherence of a line: notes connected stepwise are heard as one movement, while leaps outline a space. This is why, in part-writing theory, stepwise movement counts as the rule, and why dissonances are resolved stepwise — suspension, passing note, and neighbour note are all second-formations.
The difference between the major and minor second is decisive here. The semitone step pulls and gives direction; the whole-tone step is neutral. Where the semitones lie in a scale determines its character, and on this the differences between the church modes rest. The augmented second arises in harmonic minor between the sixth and seventh degrees and sounds striking, which is why the melodic form smooths it out.
As a combined sound, the second creates friction: in the suspension, which resolves downward, and in the cluster, where it is used as a tonal device. Upon inversion it becomes the seventh, which presents the same ratio in a wider position and thereby sounds more open.
In just intonation the major second has the ratio 9:8 or 10:9, the minor second 16:15. A distinction is made between minor, major, and augmented seconds. Melodically it is the basic step of every scale and thus the most common interval of all. Harmonically it counts as a dissonance that is resolved; in clusters, in jazz, and in the music of Impressionism it is used as a tone colour, for instance as an added ninth or in second chords without resolution.
Performance practice
When playing, distinguish clearly between whole-tone and semitone steps; whoever treats both the same blurs the key. Lead stepwise lines as one movement with a goal, not as a sequence of individual notes. And give second-clashes weight, instead of softening them — the resolution works only if the tension was audible.