40/21

Interval information
Ratio	40/21
Factorization	23 × 3-1 × 5 × 7-1
Monzo	[3 -1 1 -1⟩
Size in cents	1115.533¢
Name	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
	https://en.xen.wiki/w/File:Jid_40_21_pluck_adu_dr220.mp3; [sound info]
	Open this interval in xen-calc

40/21, is a 7-limit interval measuring about 1115.5 cents. Despite being approximated by the diminished octave in systems like septimal meantone, it 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.

See also