Gammic family

The Carlos Gamma rank-1 temperament divides 3/2 into 20 equal parts, 11 of which give a 5/4. This is closely related to the rank-2 microtemperament tempering out [-29 -11 20⟩. This temperament, gammic, takes 11 generator steps to reach 5/4, and 20 to reach 3/2. The generator in question is 1990656/1953125 = [13 5 -9⟩, which when suitably tempered is very close to 5/171 octaves, which makes for an ideal gammic tuning. As a 5-limit temperament supported by 171EDO, schismatic temperament makes for a natural comparison. Schismatic, with a wedgie of ⟨⟨ 1 -8 -15 ]] is plainly much less complex than gammic with wedgie ⟨⟨ 20 11 -29 ]], but people seeking the exotic might prefer gammic even so. The 34-note MOS is interesting, being a 1L 33s refinement of the 34EDO tuning. Of course gammic can be tuned to 34, which makes the two equivalent, and would rather remove the point of Carlos Gamma if used for it.

Because 171 is such a strong 7-limit system, it is natural to extend gammic to the 7-limit. This we may do by adding 4375/4374 to the comma list, giving a wedgie of ⟨⟨ 20 11 96 -29 96 192 ]]. 96 gammic generators finally reach 7, which is a long way to go compared to the 39 generator steps of pontiac. If someone wants to make the trip, a 103-note MOS is possible.

Gammic

Subgroup: 2.3.5

Comma: [-29 -11 20⟩

Mapping: [⟨1 1 2], ⟨0 20 11]]

POTE generator: ~1990656/1953125 = 35.0964

Badness: 0.087752

Septimal gammic

Subgroup: 2.3.5.7

Comma list: 4375/4374, 6591796875/6576668672

Mapping: [⟨1 1 2 0], ⟨0 20 11 96]]

POTE generator: ~234375/229376 = 35.0904

Badness: 0.047362

Neptune

A more interesting extension is to neptune, which divides an octave plus a gammic generator in half, to get a 10/7 generator. Neptune adds 2401/2400 to the gammic comma, and may be described as the 68&171 temperament. The generator chain goes merrily on, stacking one 10/7 over another, until after eighteen generator steps 6/5 (up nine octaves) is reached. Then in succession we get 12/7, the neutral third, 7/4 and 5/4. Two neutral thirds then gives a fifth, and these intervals with their inverses are the full set of septimal consonances. 171EDO makes a good tuning, and we can also choose to make any of the consonances besides 7/5 and 10/7 just, including the fifth, which gives a tuning extending Carlos Gamma.

Adding 385/384 or 1375/1372 to the list of commas allows for an extension to the 11-limit, where (7/5)³ equates to 11/4. This may be described as ⟨⟨ 40 22 21 -3 … ]] or 68&103, and 171 can still be used as a tuning, with val ⟨171 271 397 480 591].

Gene Ward Smith once described neptune as an analog of miracle.

Subgroup: 2.3.5.7

Comma list: 2401/2400, 48828125/48771072

Mapping: [⟨1 21 13 13], ⟨0 -40 -22 -21]]

Mapping generators: 2, ~7/5

Wedgie: ⟨⟨ 40 22 21 -58 -79 -13 ]]

POTE generator: ~7/5 = 582.452

Badness: 0.023427

11-limit

Subgroup: 2.3.5.7.11

Comma list: 385/384, 1375/1372, 78408/78125

Mapping: [⟨1 21 13 13 2], ⟨0 -40 -22 -21 3]]

POTE generator: ~7/5 = 582.475

Optimal GPV sequence: Template:Val list

Badness: 0.063602

Poseidon

Subgroup: 2.3.5.7.11

Comma list: 2401/2400, 9801/9800, 9453125/9437184

Mapping: [⟨2 2 4 5 8], ⟨0 40 22 21 -37]]

Mapping generators: ~99/70, ~99/98

POTE generator: ~99/98 = 17.545

Optimal GPV sequence: Template:Val list

Badness: 0.041727