back to list

Assymmetrical 14-tone modes in 26-tET

🔗"Paul H. Erlich" <PErlich@...>

12/18/1998 2:30:43 PM
I decided to look at the modes of the assymmetrical scale 0 2 4 6 8 10
12 14 15 17 19 21 23 25 in 26-tET -- because all octave species of this
scale is constructed of two identical heptachords, each spanning a ~4/3,
separated by either a ~4/3 or a ~3/2; and because the scale contains 10
consonant 7-limit tetrads constructed by the generic scale pattern 1, 5,
9, 12 (5 are otonal and 5 are utonal) with a maximum tuning error of 17
cents.

In my paper, I introduce the notion of a charateristic dissonance. This
is a dissonant interval which is the same generic size (same number of
scale steps) as a consonant interval. Allowing the 7-limit to define
consonance and allowing errors up to 17 cents, the 14-out-of-26 scale
has three characteristic dissonances (plus their octave inversions and
extensions). Two are "sevenths" of 554 cents instead of the usual 508
cents, and one is an "eighth" of 554 cents instead of the usual 600
cents.

None of the modes of this scale satisfy all the properties for a
strongly tonal mode according to my paper. But a few come close. The
mode

0 2 4 6 8 10 11 13 15 17 19 21 23 25

or in cents,

0 92 185 277 369 462 508 600 692 785 877 969 1062 1154

has all characteristic dissonances disjoint from the tonic tetrad (0 8
15 21), which is major. The only other mode with this property is the
minor equivalent:

0 2 4 5 7 9 11 13 15 16 18 20 22 24

or in cents

0 92 185 231 323 415 508 600 692 738 831 923 1015 1108.

The following modes have one characteristic dissonance which shares a
note with the tonic tetrad, but it approximates the 1 identity and the
11 identity when played along with the tetrad. Therefore the interval
does not disturb the stability of the tonic too much, and the mode can
be considered tonal:

major: 0 2 4 6 8 10 12 13 15 17 19 21 23 24

or in cents

0 92 185 277 369 462 554 600 692 785 877 969 1062 1108

and

minor: 0 2 3 5 7 9 11 13 15 17 18 20 22 24

or in cents

0 92 138 231 323 415 508 600 692 785 831 923 1015 1108.