Septimal minor third
| Inverse | Septimal major sixth |
|---|---|
| Name | |
| Other names | Subminor third |
| Abbreviation | s3, sm3 |
| Size | |
| Semitones | 2 2⁄3 |
| Interval class | ~2½ |
| Just interval | 7:6 |
| Cents | |
| Equal temperament | 300 |
| 24 equal temperament | 250 |
| Just intonation | 267 |
In music, the septimal minor third 
play , also called the subminor third (e.g., by Helmholtz), is the musical interval exactly or approximately equal to a 7/6 ratio of frequencies. In terms of cents, it is 267 cents, a quartertone of size 36/35 flatter than a just minor third of 6/5. In 24-tone equal temperament five quarter tones approximate the septimal minor third at 250 cents ( Play ).
The septimal minor third may be derived in the harmonic series from the seventh harmonic, and as such is in inharmonic ratios with all notes in the regular 12TET scale, with the exception of the fundamental and the octave. It has a darker but generally pleasing character when compared to the 6/5 third. A triad formed by using it in place of the minor third is called a septimal minor or subminor triad play .
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