40/21
40/21, the acute major seventh, is a 7-limit interval measuring about 1115.5 cents. Despite being approximated by the diminished octave in systems like septimal meantone, and even being called the "small septimal diminished octave" by some musicians due to analogy with 21/20 being called the "large septimal chroma", 40/21 is a major seventh in both Helmholtz-Ellis notation and Functional Just System because it is sharp of the Pythagorean major seventh (243/128) by 5120/5103.
| Interval information |
small septimal diminished octave
[sound info]