40/21: Difference between revisions

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'''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 through 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 [[243/128|Pythagorean major seventh (243/128)]] by [[5120/5103]].  
'''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 [[243/128|Pythagorean major seventh (243/128)]] by [[5120/5103]].  


== See also ==
== See also ==

Revision as of 15:14, 25 December 2020

Interval information
Ratio 40/21
Factorization 23 × 3-1 × 5 × 7-1
Monzo [3 -1 1 -1
Size in cents 1115.533¢
Names acute major seventh,
small septimal diminished octave
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]
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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.

See also