22/21: Difference between revisions

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'''22/21''' is a small [[superparticular]] [[semitone (interval region)|semitone]] of about 80.5¢ that appears in [[11-limit]] [[just intonation]], commonly known as the '''small undecimal semitone''', or '''undecimal minor semitone'''. It is the difference between [[12/11]] and [[8/7]], or between [[7/6]] and [[11/9]].
'''22/21''' is a small [[superparticular]] [[semitone]] of about 80.5¢ that appears in [[11-limit]] [[just intonation]], commonly known as the '''small undecimal semitone''', or '''undecimal minor semitone'''. It makes the difference between the 21st and 22nd [[harmonic]]s.  


In many notation systems (e.g. [[FJS]], [[HEJI]]), it is an imperfect unison, as it is the stack of an [[33/32|undecimal quartertone (33/32)]] and a [[64/63|septimal comma (64/63)]], neither of which changes the [[scale|scale degree]] or [[interval quality|quality]]. However, it is only flat of the [[256/243|Pythagorean minor second (256/243)]] by a [[896/891|pentacircle comma (896/891)]]. For this reason it could be called the '''pentacircle minor second'''.  
In many notation systems (e.g. [[FJS]], [[HEJI]]), it is an imperfect unison, as it is the stack of an [[33/32|undecimal quartertone (33/32)]] and a [[64/63|septimal comma (64/63)]], neither of which changes the [[scale|scale degree]] or [[interval quality|quality]]. However, it is only flat of the [[256/243|Pythagorean minor second (256/243)]] by a [[896/891|pentacircle comma (896/891)]]. For this reason it could be called the '''pentacircle minor second'''.  


Furthermore, it is close in size to [[21/20]], a 7-limit superparticular interval most commonly treated as a minor second, differing from it by [[441/440]], about 3.9¢. The single degree of [[88cET]] can function as both 21/20 and 22/21, thus [[tempering out]] 441/440.  
Furthermore, it is close in size to [[21/20]], a 7-limit superparticular interval most commonly treated as a minor second, differing from it by [[441/440]], about 3.9¢. The single degree of [[88cET]] can function as both 21/20 and 22/21, thus [[tempering out]] 441/440.


== Approximation ==
== Approximation ==
10 steps of [[149edo]] appoximate 22/21 with a precision of about 1 part in 15 million, or 1 part in 100000 when measured using [[relative cent]]s.
10 steps of [[149edo]] appoximate 22/21 with a precision of about 1 part in 15 million, or 1 part in 100000 when measured using [[relative cent]]s.
{{Interval edo approximation|22/21}}


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

Latest revision as of 13:01, 3 November 2025

Interval information
Ratio 22/21
Factorization 2 × 3-1 × 7-1 × 11
Monzo [1 -1 0 -1 1
Size in cents 80.53704¢
Names small undecimal semitone,
undecimal minor semitone,
pentacircle minor second
Color name 1or1, loru unison
FJS name [math]\displaystyle{ \text{P1}^{11}_{7} }[/math]
Special properties superparticular,
reduced
Tenney norm (log2 nd) 8.85175
Weil norm (log2 max(n, d)) 8.91886
Wilson norm (sopfr(nd)) 23
Comma size medium

[sound info]
Open this interval in xen-calc

22/21 is a small superparticular semitone of about 80.5¢ that appears in 11-limit just intonation, commonly known as the small undecimal semitone, or undecimal minor semitone. It is the difference between 12/11 and 8/7, or between 7/6 and 11/9.

In many notation systems (e.g. FJS, HEJI), it is an imperfect unison, as it is the stack of an undecimal quartertone (33/32) and a septimal comma (64/63), neither of which changes the scale degree or quality. However, it is only flat of the Pythagorean minor second (256/243) by a pentacircle comma (896/891). For this reason it could be called the pentacircle minor second.

Furthermore, it is close in size to 21/20, a 7-limit superparticular interval most commonly treated as a minor second, differing from it by 441/440, about 3.9¢. The single degree of 88cET can function as both 21/20 and 22/21, thus tempering out 441/440.

Approximation

10 steps of 149edo appoximate 22/21 with a precision of about 1 part in 15 million, or 1 part in 100000 when measured using relative cents.

Edo approximations for 22/21 (80.54 ¢)
≤ 80edo, relative error ≤ 10%
Edo Step size Cents (¢) Absolute error (¢) Relative error (%)
14 1\14 85.71 +5.18 +6.04
15 1\15 80.00 -0.54 -0.67
16 1\16 75.00 -5.54 -7.38
29 2\29 82.76 +2.22 +5.37
30 2\30 80.00 -0.54 -1.34
31 2\31 77.42 -3.12 -8.05
44 3\44 81.82 +1.28 +4.70
45 3\45 80.00 -0.54 -2.01
46 3\46 78.26 -2.28 -8.73
59 4\59 81.36 +0.82 +4.03
60 4\60 80.00 -0.54 -2.69
61 4\61 78.69 -1.85 -9.40
74 5\74 81.08 +0.54 +3.35
75 5\75 80.00 -0.54 -3.36

See also