9/5: Difference between revisions

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{{Infobox Interval
{{Infobox Interval
| Ratio = 9/5
| Name = just minor seventh, classic(al) minor seventh, ptolemaic minor seventh
| Monzo = 0 2 -1
| Cents = 1017.5963
| Name = just minor seventh, <br>classic minor seventh
| Color name = g7, gu 7th
| Color name = g7, gu 7th
| FJS name = m7<sub>5</sub>
| Sound = jid_9_5_pluck_adu_dr220.mp3
| Sound = jid_9_5_pluck_adu_dr220.mp3
}}
}}
{{Wikipedia|Minor seventh}}
{{Wikipedia|Minor seventh}}


'''9/5''' is a treated as a consonance in [[5-limit]] [[just intonation]], forming a part of such chords such as the 1-6/5-3/2-9/5 minor seventh chord, and the supermajor tetrad, 1-9/7-3/2-9/5 in the 7-limit.
'''9/5''', the '''just''', '''classic(al)''', or '''ptolemaic minor seventh'''<ref>For reference, see [[5-limit]]. </ref> is often treated as a consonance in [[5-limit]] [[just intonation]], forming a part of such chords such as the 1-6/5-3/2-9/5 minor seventh chord, and the supermajor tetrad, 1-9/7-3/2-9/5 in the 7-limit.


Coincidentally, the ratio between a common "alternative" tuning frequency (A432) and the most common AC electrical frequency (60hz) is exactly 36/5, two octaves above 9/5. This is notably a more consonant interval than the 11/6 formed by the more common tuning frequency of A440, which may lead to a noticeable improvement in consonance when electrically powered instruments or amplifiers are interfered with by AC power.
Coincidentally, the ratio between a common "alternative" tuning frequency (A432) and the most common North American AC electrical frequency (60hz) is exactly 36/5, two octaves above 9/5. This is notably a more consonant interval than the 11/6 formed by the more common tuning frequency of A440, which may lead to a noticeable improvement in consonance when electrically powered instruments or amplifiers are interfered with by AC power.{{dubious}}
== Approximation ==
{{Interval edo approximation|9/5}}


== See also ==
== See also ==
* [[10/9]] – its [[octave complement]]
* [[10/9]] – its [[octave complement]]
* [[5/3]] – its [[twelfth complement]]
* [[Ed9/5]]
* [[Gallery of just intervals]]
* [[Gallery of just intervals]]


[[Category:5-limit]]
== Notes ==
<references/>
 
[[Category:Seventh]]
[[Category:Seventh]]
[[Category:Minor seventh]]
[[Category:Minor seventh]]
[[Category:Over-5]]
[[Category:Over-5 intervals]]
{{todo|expand|review interval name}}

Latest revision as of 14:15, 7 June 2026

Interval information
Ratio 9/5
Factorization 32 × 5-1
Monzo [0 2 -1
Size in cents 1017.596¢
Names just minor seventh,
classic(al) minor seventh,
ptolemaic minor seventh
Color name g7, gu 7th
FJS name [math]\displaystyle{ \text{m7}_{5} }[/math]
Special properties reduced
Tenney norm (log2 nd) 5.49185
Weil norm (log2 max(n, d)) 6.33985
Wilson norm (sopfr(nd)) 11

[sound info]
Open this interval in xen-calc
English Wikipedia has an article on:

9/5, the just, classic(al), or ptolemaic minor seventh[1] is often treated as a consonance in 5-limit just intonation, forming a part of such chords such as the 1-6/5-3/2-9/5 minor seventh chord, and the supermajor tetrad, 1-9/7-3/2-9/5 in the 7-limit.

Coincidentally, the ratio between a common "alternative" tuning frequency (A432) and the most common North American AC electrical frequency (60hz) is exactly 36/5, two octaves above 9/5. This is notably a more consonant interval than the 11/6 formed by the more common tuning frequency of A440, which may lead to a noticeable improvement in consonance when electrically powered instruments or amplifiers are interfered with by AC power.[dubiousdiscuss]

Approximation

Edo approximations for 9/5 (1017.60 ¢)
≤ 80edo, relative error ≤ 10%
Edo Step size Cents (¢) Absolute error (¢) Relative error (%)
6 5\6 1000.00 -17.60 -8.80
7 6\7 1028.57 +10.98 +6.40
13 11\13 1015.38 -2.21 -2.40
20 17\20 1020.00 +2.40 +4.01
26 22\26 1015.38 -2.21 -4.79
33 28\33 1018.18 +0.59 +1.61
39 33\39 1015.38 -2.21 -7.19
40 34\40 1020.00 +2.40 +8.01
46 39\46 1017.39 -0.20 -0.79
52 44\52 1015.38 -2.21 -9.58
53 45\53 1018.87 +1.27 +5.62
59 50\59 1016.95 -0.65 -3.18
66 56\66 1018.18 +0.59 +3.22
72 61\72 1016.67 -0.93 -5.58
73 62\73 1019.18 +1.58 +9.62
79 67\79 1017.72 +0.13 +0.82

See also

Notes

  1. For reference, see 5-limit.