Diatonic major second
| Interval information |
reduced,
reduced harmonic
The diatonic major second (M2), represented by the frequency ratio 9/8, is the larger of the two seconds (1-step intervals) in the MOS form of the diatonic scale. It is generated by stacking 2 fifths and octave-reducing. In Pythagorean tuning (and thus purely-tuned just intonation), it is approximately 203.9 cents in size, but as an interval in the abstract diatonic scale it may range from 171 to 240 cents, depending on the tuning.
It functions as the large step of diatonic, and along with the diatonic semitone (diatonic minor second) may be used to construct other diatonic intervals. For example, the diatonic major third is two major seconds stacked, and the diatonic minor third is a major second stacked with a minor second. The chromatic semitone is the difference between these two intervals.
As a harmonic interval, the diatonic major second is considered a dissonance in most contexts, due to its small size, but can in some contexts (such as arto and tendo theory) be considered a consonance or ambisonance. In 5edo, it is a consonant 8/7 interval much like the chromatic semitone.
Scale info
The diatonic scale contains five major seconds. In the Ionian mode, major seconds are found on the 1st, 2nd, 4th, 5th, and 6th degrees of the scale; the other two degrees have minor seconds. The large number of major seconds compared to minor seconds ensures that thirds that include minor seconds (that is, minor thirds) are roughly evenly distributed with major thirds; in a scale with three small steps and four large steps, for example, six out of the seven thirds are minor.
Just intonation
The diatonic major second is the smallest 3-limit superparticular interval and the 3rd square particular, denoted S3. When tempered out, it leads to the very inaccurate antitonic temperament.
