- Not to be confused with Dyad.
A dyadic chord is a chord each of whose intervals belongs to a specified set of intervals considered to be consonant; it is therefore relative to the set of intervals in question. Such a chord may also be described as dyadically or pairwise consonant.
For example, the tetrad
is a dyadic chord in the 7-odd-limit since every interval involved in it is an element of the 7-odd-limit tonality diamond. Now if we replace 7/5 with 10/7:
is not a dyadic chord in the 7-odd-limit. Although each note is 7-odd-limit over the bass, the interval between 10/7 and 6/5 is 25/21, and that between 10/7 and 8/5 is 28/25 – these are not 7-odd-limit.
The significance of dyadic chords and of the paradigm where all interval pairs are examined in the chord has the psychoacoustic basis of timbral fusion and emergence of the virtual fundamental. In the above examples, it can be shown that the lower harmonics of each note in the first chord blends better than in the second. Meanwhile, the virtual fundamental of the first chord appears 5/1 below the bass, whereas that of the second appears much lower, at 35/1 below the bass as the denominators "fight" each other. For these reasons we tend to find the first chord more consonant than the second.
Essentially tempered dyadic chord
In regular temperament theory, we may speak of a just or tempered dyadic chord. By a just dyadic chord is meant a chord in rational intonation which is dyadic, so that each of its notes in relation to the lowest note is a rational number belonging to the set of consonances, and moreover each interval between the notes belongs to the set of consonances. By an essentially just dyadic chord is meant a chord which is considered to be an approximation of a just dyadic chord, such that each of its intervals is considered to be an approximation of the corresponding interval in the just dyadic chord. So, for instance, 1-5/4-3/2 is a just dyadic chord when the consonance set is the 5-odd-limit diamond with octave equivalence, and 0-10-18 in 31edo with consonance set {8, 10, 13, 18, 21, 23, 31} modulo 31 is an essentially just dyadic chord approximating 1-5/4-3/2.
A more in-depth work-through of the starling 1-6/5-10/7 essentially tempered chord example
By an essentially tempered dyadic chord is meant a chord defined in an abstract regular temperament such that each interval belongs to a consonance set, but there is no corresponding just dyadic chord. This means there is no just chord such that each interval, when mapped by the abstract regular temperament, belongs to the consonance set. For example, the chord 1-6/5-10/7, when mapped by starling temperament, which makes 126/125 vanish, has each of its intervals in the set of 7-odd-limit consonances which is the tempering of the 7-odd-limit diamond by 126/125 (this is because 10/7 is off from 36/25 by 126/125, and therefore 10/7 and 36/25 are tempered together in starling temperament, and since 36/25 = (6/5)², the interval from 6/5 to 10/7 in starling may be heard as a second move by 6/5). However, (10/7)/(6/5) = 25/21 is 25-odd-limit, and there is no other 7-odd-limit just dyadic chord which can be used instead to give the result, so it is an essentially tempered dyadic chord. Essentially tempered dyadic chords are a related notion to comma pumps, and can be used as a basis for creating pumps. Using essentially tempered chords in chord progressions breaks the harmony out of exclusively just chord relations, and serves as a sort of harmonic lubricant imparting fluidity and dynamism to the harmony, at the cost fairly often of some blurring of the sense of tonality.
Innate comma chord
An innate comma chord, proposed by Kite Giedraitis, is the type of chord that cannot be mapped to just intonation in a given prime limit and odd limit, hence a chord that will not "ring". This is broader than the essentially tempered chord because it includes the possibility that the chord is not tempered at all, and contains a wolf interval. For example, the augmented triad in 5-limit JI is an innate comma chord, because it is impossible to tune all three major 3rds to 5/4. The innate comma here is 128/125 = 41¢. In practice, it might be sung or played justly, but with a large odd limit and hence a wolf interval, as 1/1 - 5/4 - 25/16 or 1/1 - 5/4 - 8/5. Or it might be tempered, e.g. in 12-edo as 0¢ - 400¢ - 800¢ - 1200¢. In 7-limit JI, one of the 3rds can be tuned to 9/7. The innate comma is reduced to 225/224, only 8¢. This comma can be distributed among the three 3rds, resulting in tempering each only a few cents, which may be close enough to be acceptable. In 11-limit JI, this chord isn't an innate comma chord, because it can be tuned justly as 7:9:11, a low enough odd limit to "ring". However, it's debatable that this chord qualifies as an augmented triad, because the upper 3rd hardly sounds major.
Anomalous saturated suspension
An anomalous saturated suspension (ASS), introduced by Graham Breed[1], is a q-odd-limit just dyadic chord to which no pitch q-odd-limit pitch class can be added while keeping it in the q-odd-limit, and which is neither an otonal or a utonal chord; that is, it is not contained as a subchord of either the 1:3:5:…:q chord or the 1:1/3:1/5:…:1/q chord. The existence of such chords was discovered by Paul Erlich[2]. Below are listed two 9-odd-limit ASSes of special interest, as they avoid intervals smaller than a minor whole tone.
For a complete list of ASS chords through the 23-odd-limit see List of anomalous saturated suspensions.
List of just intonation tetrads
List of essentially tempered dyadic chords
Here are some pages on certain essentially tempered dyadic chords, sorted by odd limit. See Dyadic chord/Pattern of essentially tempered chords for some notable abstract chord patterns.
7-odd-limit
9-odd-limit
11-odd-limit
| Chords |
Associated Temperament |
Associated Commas
|
| Mothwellsmic chords |
Mothwellsmic |
99/98
|
| Ptolemismic chords |
Ptolemismic |
100/99
|
| Biyatismic chords |
Biyatismic |
121/120
|
| Valinorsmic chords |
Valinorsmic |
176/175
|
| Rastmic chords |
Rastmic |
243/242
|
| Keenanismic chords |
Keenanismic |
385/384
|
| Werckismic chords |
Werckismic |
441/440
|
| Swetismic chords |
Swetismic |
540/539
|
| Pentacircle chords |
Pentacircle |
896/891
|
| Undecimal marvel chords |
Marvel |
225/224, 385/384
|
| Prodigy chords |
Prodigy |
225/224, 441/440
|
| Undecimal sensamagic chords |
Sensamagic |
245/243, 385/384
|
| Jove chords |
Jove |
243/242, 441/440
|
| Miracle chords |
Miracle |
225/224, 243/242, 385/384
|
| Magic chords |
Magic |
100/99, 225/224, 245/243
|
| Magical seventh chord |
Supermagic |
100/99, 385/384
|
| Orwell tetrad |
Guanyin |
176/175, 540/539
|
| Tutonic hexads |
Meantone |
81/80, 99/98, 126/125
|
| Baldanders hexads |
Andromeda |
100/99, 225/224, 245/242
|
| Porcupine heptad |
Porkypine |
55/54, 100/99
|
13-odd-limit
15-odd-limit
17-odd-limit
19-odd-limit
21-odd-limit
23-odd-limit
25-odd-limit
27-odd-limit
29-odd-limit
31-odd-limit
33-odd-limit
35-odd-limit
37-odd-limit
39-odd-limit
55-odd-limit
List of essentially just dyadic chords
As chords that are unambiguous counterparts to common JI chords are not of particular relevance to this page, most of the entries here will be what Kaiveran calls plurichords, where there are multiple sets of consonances that a given chord can be mapped to. Note that this can still lead to ambiguous tonality in the case of otonal and utonal intervals being identified together.
See also
Notes
