Aberrismic theory
groundfault's aberrismic theory is a xen theory paradigm using aberrismas, a type of scale step which can be added to a scale pattern to turn it into a scale of one rank higher. The aberrisma is a new category of melodic steps that are smaller than the steps in the original scale, which are prototypically categorical "seconds" such as whole tones and semitones. The typical range for an aberrisma is 20 to 60 cents; groundfault holds the optimal melodic size for an aberrisma to be approximately 40 cents. Examples of ternary patterns that can be made by adding aberrismas to diatonic scales are:
- pinedye (5L2m1s or 1s)
- diasem (5L2m2s or 2s)
- blackdye (5L2m3s or 3s)
- diamech (5L2m4s or 4s)
- 5L2m5s (or 5s)
Aberrismic theory and RTT
Certain scales with aberrismas may be endowed with JI interpretations via RTT temperaments, such as equal temperaments. Under groundfault's use of RTT, the aberrisma tends to become 81/80 in a 2.3.5 context and a 64/63 in a 2.3.7 context. Thus aberrismic scales that admit more accurate 2.3.5.7 temperament interpretations and temper neither 81/80 nor 64/63, such as 5L2m5s, tend to identify 81/80 and 64/63, tempering out 5120/5103.
At times, a scale pattern has varying temperaments according to the tuning. For example, 5L2m3s may be given the temperament structure of either untempered 2.3.5 or Flutterpyth temperament.
Example: blackdye
The following table shows two different temperament interpretations for the same aberrismic scale pattern blackdye (sLmLsLmLsL), under untempered 2.3.5 and Flutterpyth respectively.
- Untempered does not mean that the final tuning must be the JI tuning, but simply that there exists a tuning with no deviation from JI, or that the temperament before applying the tuning map has the same rank as the JI subgroup.
- Flutterpyth, 2.3.7.11.13[32 & 37], is a rank-2 diatonic temperament that tempers out 64/63 like Superpyth but tunes the 3/2 even sharper, as a result tempering C-D# to a 14/11 and C-Fb to a 13/11. 37edo provides a nearly optimal tuning.
| Interval class | Sizes | Untempered 2.3.5 | Flutterpyth |
|---|---|---|---|
| 1-step | s m L |
81/80 16/15 10/9 |
143/140 22/21 160/143 |
| 2-step | L + s L + m |
9/8 32/27 |
8/7, 9/8 7/6 |
| 3-step | L + 2s L + m + s 2L + s 2L + m |
729/640 6/5 5/4 320/243 |
7/6 13/11 14/11 13/10 |
| 4-step | 2L + 2s 2L + m + s |
81/64 4/3 |
13/10 4/3 |
| 5-step | 2L + m + 2s 2L + 2m + s 3L + 2s 3L + m + s |
27/20 64/45 45/32 40/27 |
66/49 11/8 16/11 49/33 |
| 6-step | 3L + m + 2s 3L + 2m + s |
3/2 128/81 |
3/2 20/13 |
| 7-step | 3L + m + 3s 3L + 2m + 2s 4L + m + 2s 4L + 2m + s |
243/160 8/5 5/3 1280/729 |
20/13 11/7 22/13 12/7 |
| 8-step | 4L + m + 3s 4L + 2m + 2s |
27/16 16/9 |
12/7 7/4 |
| 9-step | 5L + 2m + s 5L + m + 2s 4L + 2m + 2s |
9/5 15/8 160/81 |
143/80 21/11 280/143 |