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Scale 81: "Disian"

Scale 81: Disian, Ian Ring Music Theory

Bracelet Diagram

The bracelet shows tones that are in this scale, starting from the top (12 o'clock), going clockwise in ascending semitones. The "i" icon marks imperfect tones that do not have a tone a fifth above. Dotted lines indicate axes of symmetry.

Tonnetz Diagram

Tonnetz diagrams are popular in Neo-Riemannian theory. Notes are arranged in a lattice where perfect 5th intervals are from left to right, major third are northeast, and major 6th intervals are northwest. Other directions are inverse of their opposite. This diagram helps to visualize common triads (they're triangles) and circle-of-fifth relationships (horizontal lines).

Common Names




Cardinality is the count of how many pitches are in the scale.

3 (tritonic)

Pitch Class Set

The tones in this scale, expressed as numbers from 0 to 11


Forte Number

A code assigned by theorist Allen Forte, for this pitch class set and all of its transpositional (rotation) and inversional (reflection) transformations.


Rotational Symmetry

Some scales have rotational symmetry, sometimes known as "limited transposition". If there are any rotational symmetries, these are the intervals of periodicity.


Reflection Axes

If a scale has an axis of reflective symmetry, then it can transform into itself by inversion. It also implies that the scale has Ridge Tones. Notably an axis of reflection can occur directly on a tone or half way between two tones.



A palindromic scale has the same pattern of intervals both ascending and descending.



A chiral scale can not be transformed into its inverse by rotation. If a scale is chiral, then it has an enantiomorph.

enantiomorph: 321


A hemitone is two tones separated by a semitone interval. Hemitonia describes how many such hemitones exist.

0 (anhemitonic)


A cohemitone is an instance of two adjacent hemitones. Cohemitonia describes how many such cohemitones exist.

0 (ancohemitonic)


An imperfection is a tone which does not have a perfect fifth above it in the scale. This value is the quantity of imperfections in this scale.



Modes are the rotational transformations of this scale. This number does not include the scale itself, so the number is usually one less than its cardinality; unless there are rotational symmetries then there are even fewer modes.


Prime Form

Describes if this scale is in prime form, using the Rahn/Ring formula.

prime: 69


Indicates if the scale can be constructed using a generator, and an origin.


Deep Scale

A deep scale is one where the interval vector has 6 different digits.


Interval Structure

Defines the scale as the sequence of intervals between one tone and the next.

[4, 2, 6]

Interval Vector

Describes the intervallic content of the scale, read from left to right as the number of occurences of each interval size from semitone, up to six semitones.

<0, 1, 0, 1, 0, 1>

Interval Spectrum

The same as the Interval Vector, but expressed in a syntax used by Howard Hanson.


Distribution Spectra

Describes the specific interval sizes that exist for each generic interval size. Each generic <g> has a spectrum {n,...}. The Spectrum Width is the difference between the highest and lowest values in each spectrum.

<1> = {2,4,6}
<2> = {6,8,10}

Spectra Variation

Determined by the Distribution Spectra; this is the sum of all spectrum widths divided by the scale cardinality.


Maximally Even

A scale is maximally even if the tones are optimally spaced apart from each other.


Maximal Area Set

A scale is a maximal area set if a polygon described by vertices dodecimetrically placed around a circle produces the maximal interior area for scales of the same cardinality. All maximally even sets have maximal area, but not all maximal area sets are maximally even.


Interior Area

Area of the polygon described by vertices placed for each tone of the scale dodecimetrically around a unit circle, ie a circle with radius of 1.


Polygon Perimeter

Perimeter of the polygon described by vertices placed for each tone of the scale dodecimetrically around a unit circle.


Myhill Property

A scale has Myhill Property if the Interval Spectra has exactly two specific intervals for every generic interval.



A scale is balanced if the distribution of its tones would satisfy the "centrifuge problem", ie are placed such that it would balance on its centre point.


Ridge Tones

Ridge Tones are those that appear in all transpositions of a scale upon the members of that scale. Ridge Tones correspond directly with axes of reflective symmetry.



Also known as Rothenberg Propriety, named after its inventor. Propriety describes whether every specific interval is uniquely mapped to a generic interval. A scale is either "Proper", "Strictly Proper", or "Improper".


Heteromorphic Profile

Defined by Norman Carey (2002), the heteromorphic profile is an ordered triple of (c, a, d) where c is the number of contradictions, a is the number of ambiguities, and d is the number of differences. When c is zero, the scale is Proper. When a is also zero, the scale is Strictly Proper.

(0, 1, 6)

Common Triads

There are no common triads (major, minor, augmented and diminished) that can be formed using notes in this scale.


Modes are the rotational transformation of this scale. Scale 81 can be rotated to make 2 other scales. The 1st mode is itself.

2nd mode:
Scale 261
Scale 261: Bozian, Ian Ring Music TheoryBozian
3rd mode:
Scale 1089
Scale 1089: Gocian, Ian Ring Music TheoryGocian


The prime form of this scale is Scale 69

Scale 69Scale 69: Dezian, Ian Ring Music TheoryDezian


The tritonic modal family [81, 261, 1089] (Forte: 3-8) is the complement of the enneatonic modal family [1503, 1917, 2007, 2799, 3051, 3447, 3573, 3771, 3933] (Forte: 9-8)


The inverse of a scale is a reflection using the root as its axis. The inverse of 81 is 321

Scale 321Scale 321: Cahian, Ian Ring Music TheoryCahian


Only scales that are chiral will have an enantiomorph. Scale 81 is chiral, and its enantiomorph is scale 321

Scale 321Scale 321: Cahian, Ian Ring Music TheoryCahian


In the abbreviation, the subscript number after "T" is the number of semitones of tranposition, "M" means the pitch class is multiplied by 5, and "I" means the result is inverted. Operation is an identical way to express the same thing; the syntax is <a,b> where each tone of the set x is transformed by the equation y = ax + b

Abbrev Operation Result Abbrev Operation Result
T0 <1,0> 81       T0I <11,0> 321
T1 <1,1> 162      T1I <11,1> 642
T2 <1,2> 324      T2I <11,2> 1284
T3 <1,3> 648      T3I <11,3> 2568
T4 <1,4> 1296      T4I <11,4> 1041
T5 <1,5> 2592      T5I <11,5> 2082
T6 <1,6> 1089      T6I <11,6> 69
T7 <1,7> 2178      T7I <11,7> 138
T8 <1,8> 261      T8I <11,8> 276
T9 <1,9> 522      T9I <11,9> 552
T10 <1,10> 1044      T10I <11,10> 1104
T11 <1,11> 2088      T11I <11,11> 2208
Abbrev Operation Result Abbrev Operation Result
T0M <5,0> 321      T0MI <7,0> 81
T1M <5,1> 642      T1MI <7,1> 162
T2M <5,2> 1284      T2MI <7,2> 324
T3M <5,3> 2568      T3MI <7,3> 648
T4M <5,4> 1041      T4MI <7,4> 1296
T5M <5,5> 2082      T5MI <7,5> 2592
T6M <5,6> 69      T6MI <7,6> 1089
T7M <5,7> 138      T7MI <7,7> 2178
T8M <5,8> 276      T8MI <7,8> 261
T9M <5,9> 552      T9MI <7,9> 522
T10M <5,10> 1104      T10MI <7,10> 1044
T11M <5,11> 2208      T11MI <7,11> 2088

The transformations that map this set to itself are: T0, T0MI

Nearby Scales:

These are other scales that are similar to this one, created by adding a tone, removing a tone, or moving one note up or down a semitone.

Scale 83Scale 83: Amuian, Ian Ring Music TheoryAmuian
Scale 85Scale 85: Segian, Ian Ring Music TheorySegian
Scale 89Scale 89: Aggian, Ian Ring Music TheoryAggian
Scale 65Scale 65: Tritone, Ian Ring Music TheoryTritone
Scale 73Scale 73: Diminished Triad, Ian Ring Music TheoryDiminished Triad
Scale 97Scale 97: Athian, Ian Ring Music TheoryAthian
Scale 113Scale 113, Ian Ring Music Theory
Scale 17Scale 17: Major Third Ditone, Ian Ring Music TheoryMajor Third Ditone
Scale 49Scale 49: Aguian, Ian Ring Music TheoryAguian
Scale 145Scale 145: Raga Malasri, Ian Ring Music TheoryRaga Malasri
Scale 209Scale 209: Birian, Ian Ring Music TheoryBirian
Scale 337Scale 337: Koptic, Ian Ring Music TheoryKoptic
Scale 593Scale 593: Saric, Ian Ring Music TheorySaric
Scale 1105Scale 1105: Messiaen Truncated Mode 6 Inverse, Ian Ring Music TheoryMessiaen Truncated Mode 6 Inverse
Scale 2129Scale 2129: Raga Nigamagamini, Ian Ring Music TheoryRaga Nigamagamini

This scale analysis was created by Ian Ring, Canadian Composer of works for Piano, and total music theory nerd. Scale notation generated by VexFlow, graph visualization by Graphviz, and MIDI playback by MIDI.js. All other diagrams and visualizations are © Ian Ring. Some scale names used on this and other pages are ©2005 William Zeitler ( used with permission.

Pitch spelling algorithm employed here is adapted from a method by Uzay Bora, Baris Tekin Tezel, and Alper Vahaplar. (An algorithm for spelling the pitches of any musical scale) Contact authors Patent owner: Dokuz Eylül University, Used with Permission. Contact TTO

Tons of background resources contributed to the production of this summary; for a list of these peruse this Bibliography. Special thanks to Richard Repp for helping with technical accuracy, and George Howlett for assistance with the Carnatic ragas.