Minor triad
Root, minor third, perfect fifth. A single semitone distinguishes it from major.
What it means
The minor triad consists of root, minor third, and perfect fifth; between the third and the fifth there accordingly lies a major third. In A minor, A–C–E is the minor triad on the tonic. It differs from the major triad only in the third, which lies a semitone lower — this one note decides the mode.
Musical use
In the major key, minor triads stand diatonically on the second, third, and sixth degrees. In function theory they count as representatives of the main functions: the sonority on the sixth degree is the tonic's relative, the one on the second degree the subdominant's relative, the one on the third degree is interpreted, depending on context, as the dominant's relative or as the tonic's counter-chord. From this arise the possibilities of substitution that make possible, for instance, the deceptive cadence, in which the chord of the sixth degree appears instead of the tonic.
In minor, the minor triad is the tonic and also stands diatonically on the fourth degree as the subdominant. The dominant, too, is a minor sonority in the natural form; for the cadence it is made into a major sonority by raising the seventh degree, so that a leading tone results.
Acoustically the minor triad is less simply grounded than the major triad, because the minor third above the tonic appears only later in the harmonic series. This has occupied theory for a long time, without a generally accepted explanation having been found.
The minor triad cannot be derived directly from the lower overtones as the major triad can, which has led to various explanations in the history of theory. In major it stands on the second, third, and sixth degrees; in function theory these are the relatives and counter-chords. In minor it forms the tonic and subdominant.
Performance practice
Intonate the minor third rather high, so that the sonority becomes calm. In minor pieces, watch whether the dominant appears as a major or minor sonority — the leading tone stands only within the bar, not in the key signature. And practise distinguishing major and minor on individual chords, until it succeeds without thinking.