40/21

40/21, is a 7-limit interval which despite being dubbed the small septimal diminished octave by some musicians, is actually a type of major seventh for much the same reason that 21/20 is actually a diatonic semitone of sorts, specifically is it dubbed the acute major seventh by the Huygens-Fokker Foundation.

Interval information

Ratio	40/21
Factorization	23 × 3-1 × 5 × 7-1
Monzo	[3 -1 1 -1⟩
Size in cents	1115.533¢
Names	small septimal suboctave, acute major seventh
FJS name	[math]\displaystyle{ \text{M7}^{5}_{7} }[/math]
Special properties	reduced
Tenney norm (log2 nd)	9.71425
Weil norm (log2 max(n, d))	10.6439
Wilson norm (sopfr(nd))	21
[sound info]
Open this interval in xen-calc

See also

• 21/20 – its octave complement