28/15: Difference between revisions

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{{Infobox Interval
{{Infobox Interval
| Ratio = 28/15
| Name = septimal grave major seventh, aberschismic diminished octave
| Monzo = 2 -1 -1 1
| Color name = zg8, zogu octave
| Cents = 1080.55719
| Name = septimal grave major seventh
| Color name =  
| FJS name = d8<sup>7</sup><sub>5</sub>
| Sound = jid_28_15_pluck_adu_dr220.mp3
| Sound = jid_28_15_pluck_adu_dr220.mp3
}}
}}
'''28/15''' is an interval in [[7-limit]] [[just intonation]] measuring about 1080.6 [[cent]]s, traditionally known as the '''septimal grave major seventh''' for its proximity (and conflation in [[marvel]] tunings such as septimal [[meantone]]) with the classical major seventh [[15/8]]. However, it functions as a diminished octave, as is supported by [[Sagittal notation]], [[Helmholtz–Ellis notation]] and the [[Functional Just System]], viewed as the [[4096/2187|Pythagorean diminished octave]] flattened by an [[aberschisma]]. This gives rise to the more precise name '''aberschismic diminished octave'''. It arises from stacking various [[9-odd-limit]] consonances, including the stack consisting of [[6/5]] and [[14/9]], of [[7/6]] and [[8/5]], and of [[7/5]] and [[4/3]].


'''28/15''' is a [[7-limit]] [[just intonation]] interval of about 1080.6 [[cent]]s. It is well approximated by [[10edo]] (9\10).  
== Approximation ==
This interval is well approximated by [[10edo]] (9\10).  


== Terminology ==
{{Interval edo approximation|28/15}}
Despite being approximated by the major seventh in systems like [[septimal meantone]], and even being called the '''septimal grave major seventh''' by some musicians, 28/15 is a diminished octave in just intonation notation systems such as [[Sagittal notation]], [[Helmholtz-Ellis notation]] and the [[Functional Just System]], viewed as the Pythagorean diminished octave ([[4096/2187]]) altered by [[5120/5103]].


== See also ==
== See also ==
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* [[Gallery of just intervals]]
* [[Gallery of just intervals]]


[[Category:7-limit]]
[[Category:Seventh]]
[[Category:Seventh]]
[[Category:Major seventh]]
[[Category:Major seventh]]
[[Category:Octave]]
[[Category:Octave]]
[[Category:Diminished octave]]
[[Category:Diminished octave]]
[[Category:Pages with internal sound examples]]
{{todo| expand | improve synopsis | add color name }}

Latest revision as of 10:46, 1 August 2026

Interval information
Ratio 28/15
Factorization 22 × 3-1 × 5-1 × 7
Monzo [2 -1 -1 1
Size in cents 1080.557¢
Names septimal grave major seventh,
aberschismic diminished octave
Color name zg8, zogu octave
FJS name [math]\displaystyle{ \text{d8}^{7}_{5} }[/math]
Special properties reduced
Tenney norm (log2 nd) 8.71425
Weil norm (log2 max(n, d)) 9.61471
Wilson norm (sopfr(nd)) 19

[sound info]
Open this interval in xen-calc

28/15 is an interval in 7-limit just intonation measuring about 1080.6 cents, traditionally known as the septimal grave major seventh for its proximity (and conflation in marvel tunings such as septimal meantone) with the classical major seventh 15/8. However, it functions as a diminished octave, as is supported by Sagittal notation, Helmholtz–Ellis notation and the Functional Just System, viewed as the Pythagorean diminished octave flattened by an aberschisma. This gives rise to the more precise name aberschismic diminished octave. It arises from stacking various 9-odd-limit consonances, including the stack consisting of 6/5 and 14/9, of 7/6 and 8/5, and of 7/5 and 4/3.

Approximation

This interval is well approximated by 10edo (9\10).


Edo approximations for 28/15 (1080.56 ¢)
≤ 80edo, relative error ≤ 10%
Edo Step size Cents (¢) Absolute error (¢) Relative error (%)
10 9\10 1080.00 -0.56 -0.46
11 10\11 1090.91 +10.35 +9.49
20 18\20 1080.00 -0.56 -0.93
21 19\21 1085.71 +5.16 +9.02
30 27\30 1080.00 -0.56 -1.39
31 28\31 1083.87 +3.31 +8.56
40 36\40 1080.00 -0.56 -1.86
41 37\41 1082.93 +2.37 +8.10
50 45\50 1080.00 -0.56 -2.32
51 46\51 1082.35 +1.80 +7.63
60 54\60 1080.00 -0.56 -2.79
61 55\61 1081.97 +1.41 +7.17
70 63\70 1080.00 -0.56 -3.25
71 64\71 1081.69 +1.13 +6.70
80 72\80 1080.00 -0.56 -3.71

See also