Minor third
A
minor third is the smaller of two commonly occurring
musical intervals compounded of two steps of the
diatonic scale. The prefix 'minor' identifies it as being the smaller of the two (by one semitone); its larger counterpart being a
major third. The minor third is abbreviated as
m3 and its
inversion is the
major sixth.
The
minor scale is so named because of the presence of this interval between its
tonic and
mediant (1st and 3rd)
scale degrees.
Minor chords too, take their name from the presence of this interval built on the chord's
root (provided that the interval of a
perfect fifth from the root is also present or implied).
A minor third in
just intonation corresponds to a pitch ratio of 6:5; with other pitch ratios given related names; the
septimal minor third with ratio 7:6 and the tridecimal minor third with ratio 13:11 in particular. In an
equal tempered tuning, a minor third is equal to three
semitones, a ratio of 1:2
3/12 (approximately 1:1.189), or 300 cents, 15.641
cents smaller. In other
meantone tunings it is larger, and in
19 equal temperament it is very nearly the 6:5 ratio of just intonation.
The minor third is classed as an
imperfect consonance and is considered one of the most consonant intervals after the
unison,
octave,
perfect fifth, and
perfect fourth.
Augmented second
An
augmented second is
enharmonically equivalent to a minor third in
equal temperament, but is not the same interval in other meantone tunings. In any tuning close to
1/4 comma meantone it will be close to the 7:6 ratio of the
septimal minor third. Hence the distinction is not, as often thought and even taught, a purely formal and contextual one, but reflects the tuning practice of much of the
common practice period.
Augmented seconds occur in many scales, most importantly the
harmonic minor and its various modes. They also occur in the various "gypsy minor" scales (which consist almost entirely of augmented and
minor seconds). In harmonic minor scales, the augmented second occurs between the sixth and seventh scale degrees. For example, in the scale of
A harmonic minor, the notes
F and
G♯ form the interval of an augmented second. This distinguishing feature of harmonic minor scales occurs as a consequence of the seventh scale degree having been chromatically raised in order to allow
chords in a minor key to follow the same rules of
cadence observed in major keys, where the V chord is "dominant" (that is, contains a major triad plus a
minor seventh).
*
musical tuning*
semiditono*
List of meantone intervals*
Tonalsoft Encyclopaedia of Tuning
