# Tetracot family

The parent of the **tetracot family** is **tetracot**, the 5-limit temperament tempering out 20000/19683 = [5 -9 4⟩, the minimal diesis or tetracot comma. The dual of this comma is the wedgie ⟨⟨4 9 5]], which tells us 10/9 is a generator, and that four of them give 3/2. In fact, (10/9)^{4} = 20000/19683 × 3/2. We also have (10/9)^{9} = (20000/19683)^{2} × 5/2. From this it is evident we should flatten the generator a bit, and 34EDO does this and makes for a recommendable tuning. Another possibility is to use (5/2)^{(1/9)} for a generator. The 13-note MOS gives enough space for eight triads, with the 20-note MOS supplying many more.

The name comes from members of the Araucaria family of conifers, which have four cotyledons (though sometimes these are fused).

## Tetracot

Subgroup: 2.3.5

Comma list: 20000/19683

POTE generator: ~10/9 = 176.160

Mapping: [⟨1 1 1], ⟨0 4 9]]

Optimal GPV sequence: 7, 20c, 27, 34, 75, 109, 470b, 579b

Badness: 0.048518

### Extensions

The second comma of the normal comma list defines which 7-limit family member we are looking at.

- 875/864, the keema, gives monkey;
- 179200/177147 (or equivalently 225/224) gives bunya;
- 245/243 gives octacot, which splits the generator in half.

#### Monkey and bunya

**Monkey** tempers out the keema. The keema, 875/864, is the amount by which three just minor thirds fall short of 7/4, and tells us the 7/4 of monkey is reached by three minor thirds in succession. It can be described as the 34&41 temperament, if the vals in question are taken to be patent vals, meaning that *n*×log_{2}(prime) rounded to the nearest integer gives the mapping. 41EDO is an excellent tuning for monkey, and has the effect of making monkey identical to bunya with the same tuning.

**Bunya** adds 225/224 to the list of commas and may be described as the 41&75 temperament. 41EDO can again be used as a tuning, in which case it is the same as monkey. However an excellent alternative is 14^{(1/26)} as a generator, giving just 7s and an improved value for 5, at the cost of a slightly sharper, but still less than a cent sharp, fifth. Octave stretching, if employed, also serves to distinguish bunya from monkey, as its octaves should be stretched considerably less.

Since the generator in all cases is between 10/9 and 11/10, it is natural to extend these temperaments to the 11-limit by tempering out (10/9)/(11/10) = 100/99. This gives 11-limit monkey, ⟨⟨4 9 -15 10 …]] and 11-limit bunya, ⟨⟨4 9 26 10 …]]. Again, 41edo can be used as a tuning, making the two identical, which is also the case if we turn to the 2.3.5.11 temperament, dispensing with 7. However 11-limit bunya, like 7-limit bunya, profits a little from a slightly sharper fifth, such as the 14^{(1/26)} generator supplies, or even sharper yet, as for instance by the val ⟨355 563 823 997 1230], with a 52/355 generator.

Since 16/13 is shy of (10/9)^{2} by just 325/324, it is likewise natural to extend our winning streak with these temperaments by adding this to the list of commas. This gives us ⟨⟨4 9 -15 10 -2 …]] for 13-limit monkey and ⟨⟨4 9 26 10 -2 …]] for 13-limit bunya. Once again, 41 is recommended as a tuning for monkey, while bunya can with advantage tune the fifth sharper: 17/116 as a generator with a fifth a cent and a half sharp or 11/75 with a fifth two cents sharp.

## Monkey

Subgroup: 2.3.5.7

Comma list: 875/864, 5120/5103

Mapping: [⟨1 1 1 5], ⟨0 4 9 -15]]

Wedgie: ⟨⟨4 9 -15 5 -35 -60]]

POTE generator: ~10/9 = 175.659

Optimal GPV sequence: 7, 27d, 34, 41, 321ccdd

Badness: 0.073437

### 11-limit

Subgroup: 2.3.5.7.11

Comma list: 100/99, 243/242, 385/384

Mapping: [⟨1 1 1 5 2], ⟨0 4 9 -15 10]]

POTE generator: ~10/9 = 175.570

Optimal GPV sequence: 7, 27de, 34, 41

Badness: 0.038836

### 13-limit

Subgroup: 2.3.5.7.11.13

Comma list: 100/99, 105/104, 144/143, 243/242

Mapping: [⟨1 1 1 5 2 4], ⟨0 4 9 -15 10 -2]]

POTE generator: ~10/9 = 175.622

Optimal GPV sequence: 7, 27de, 34, 41

Badness: 0.028410

## Bunya

Subgroup: 2.3.5.7

Comma list: 225/224, 15625/15309

Mapping: [⟨1 1 1 -1], ⟨0 4 9 26]]

Wedgie: ⟨⟨4 9 26 5 30 35]]

POTE generator: ~10/9 = 175.741

Optimal GPV sequence: 34d, 41, 116, 157c, 198c

Badness: 0.062897

### 11-limit

Subgroup: 2.3.5.7.11

Comma list: 100/99, 225/224, 1344/1331

Mapping: [⟨1 1 1 -1 2], ⟨0 4 9 26 10]]

POTE generator: ~10/9 = 175.777

Optimal GPV sequence: 34d, 41, 116e, 157ce

Badness: 0.031332

### 13-limit

Subgroup: 2.3.5.7.11.13

Comma list: 100/99, 144/143, 225/224, 243/242

Mapping: [⟨1 1 1 -1 2 4], ⟨0 4 9 26 10 -2]]

POTE generator: ~10/9 = 175.886

Optimal GPV sequence: 34d, 41, 75e, 116ef

Badness: 0.024886

## Modus

Subgroup: 2.3.5.7

Comma list: 64/63, 4375/4374

Mapping: [⟨1 1 1 4], ⟨0 4 9 -8]]

POTE generator: ~10/9 = 177.203

Optimal GPV sequence: 7, 20c, 27, 61d, 88bcd

Badness: 0.068184

### 11-limit

Subgroup: 2.3.5.7.11

Comma list: 64/63, 100/99, 243/242

Mapping: [⟨1 1 1 4 2], ⟨0 4 9 -8 10]]

POTE generator: ~10/9 = 177.053

Badness: 0.035149

#### 13-limit

Subgroup: 2.3.5.7.11.13

Comma list: 64/63, 78/77, 100/99, 144/143

Mapping: [⟨1 1 1 4 2 4], ⟨0 4 9 -8 10 -2]]

POTE generator: ~10/9 = 176.953

Badness: 0.023806

- Musical examples

- Tetracot Perc-Sitar by Dustin Schallert
- Tetracot Jam by Dustin Schallert
- Tetracot Pump by Dustin Schallert all in 27edo

### Ponens

The error of 11 is about the same as that of Modus, but flat instead of sharp, and much more abundant. Since the other primes are all sharp, however, this leads to a much larger error for other intervals involving 11.

Subgroup: 2.3.5.7.11

Comma list: 55/54, 64/63, 363/350

Mapping: [⟨1 1 1 4 3], ⟨0 4 9 -8 3]]

POTE generator: ~10/9 = 177.200

Optimal GPV sequence: 7, 20c, 27, 61dee, 88bcdee

Badness: 0.063077

#### 13-limit

Subgroup: 2.3.5.7.11.13

Comma list: 55/54, 64/63, 66/65, 143/140

Mapping: [⟨1 1 1 4 3 4], ⟨0 4 9 -8 3 -2]]

POTE generator: ~10/9 = 177.197

Optimal GPV sequence: 7, 20c, 27, 61dee, 88bcdee

Badness: 0.039043

## Wollemia

Subgroup: 2.3.5.7

Comma list: 126/125, 2240/2187

Mapping: [⟨1 1 1 0], ⟨0 4 9 19]]

Wedgie: ⟨⟨4 9 19 5 19 19]]

POTE generator: ~10/9 = 177.357

Optimal GPV sequence: 27, 61, 88bc, 115bc

Badness: 0.070522

### 11-limit

Subgroup: 2.3.5.7.11

Comma list: 56/55, 100/99, 243/242

Mapping: [⟨1 1 1 0 2], ⟨0 4 9 19 10]]

POTE generator: ~10/9 = 177.413

Optimal GPV sequence: 27e, 34, 61e

Badness: 0.037551

### 13-limit

Subgroup: 2.3.5.7.11.13

Comma list: 56/55, 91/90, 100/99, 352/351

Mapping: [⟨1 1 1 0 2 4], ⟨0 4 9 19 10 -2]]

POTE generator: ~10/9 = 177.231

Optimal GPV sequence: 27e, 34, 61e

Badness: 0.031219

## Octacot

*See also: Chords of octacot*

Octacot cuts the Gordian knot of deciding between the monkey and bunya mappings for 7 by cutting the generator in half and splitting the difference. It adds 245/243 to the normal comma list, and also tempers out 2401/2400. It may also be described as 41&68. 68EDO or 109EDO can be used as tunings, as can (5/2)^{(1/18)}, which gives just major thirds. Another tuning is 150EDO, which has a generator, 11/150, of exactly 88 cents. This relates octacot to the 88cET non-octave temperament, which like Carlos Alpha arguably makes more sense viewed as part of a rank two temperament with octaves rather than rank one without them.

Once again and for the same reasons, it is natural to add 100/99 and 325/324 to the list of commas, giving ⟨⟨8 18 11 20 -4 …]] as the octave part of the wedgie. Generators of 3\41, 8\109 and 11\150 (88 cents) are all good choices for the 7, 11 and 13 limits.

Subgroup: 2.3.5.7

Comma list: 245/243, 2401/2400

Mapping: [⟨1 1 1 2], ⟨0 8 18 11]]

Wedgie: ⟨⟨8 18 11 10 -5 -25]]

POTE generator: ~21/20 = 88.076

Optimal GPV sequence: 14c, 27, 41, 68, 109

Badness: 0.033845

### 11-limit

Subgroup: 2.3.5.7.11

Comma list: 100/99, 243/242, 245/242

Mapping: [⟨1 1 1 2 2], ⟨0 8 18 11 20]]

POTE generator: ~21/20 = 87.975

Optimal GPV sequence: 27e, 41, 109e, 150e, 191e

Badness: 0.024078

#### 13-limit

Subgroup: 2.3.5.7.11.13

Comma list: 100/99, 144/143, 196/195, 243/242

Mapping: [⟨1 1 1 2 2 4], ⟨0 8 18 11 20 -4]]

POTE generator: ~21/20 = 88.106

Optimal GPV sequence: 27e, 41, 68e, 109ef

Badness: 0.023276

#### Octocat

Subgroup: 2.3.5.7.11.13

Comma list: 78/77, 91/90, 100/99, 245/242

Mapping: [⟨1 1 1 2 2 2], ⟨0 8 18 11 20 23]]

POTE generator: ~21/20 = 88.179

Optimal GPV sequence: 27e, 41f, 68ef

Badness: 0.027601

#### Octopod

Subgroup: 2.3.5.7.11.13

Comma list: 100/99, 105/104, 243/242, 245/242

Mapping: [⟨1 1 1 2 2 1], ⟨0 8 18 11 20 37]]

POTE generator: ~21/20 = 87.697

Optimal GPV sequence: 41, 137cd, 178cd

Badness: 0.028326

#### Dificot

Subgroup: 2.3.5.7.11.13

Comma list: 100/99, 243/242, 245/242, 343/338

Mapping: [⟨1 9 19 13 22 19], ⟨0 -16 -36 -22 -40 -33]]

POTE generator: ~13/9 = 643.989

Optimal GPV sequence: 13cdeef, 28ccdef, 41

Badness: 0.051876

## Dodecacot

Subgroup: 2.3.5.7

Comma list: 3125/3087, 10976/10935

Mapping: [⟨1 1 1 1], ⟨0 12 27 37]]

Wedgie: ⟨⟨12 27 37 15 25 10]]

POTE generator: ~28/27 = 58.675

Optimal GPV sequence: 41, 143d, 184, 225, 409bcd

Badness: 0.119761