“Sorores” (“sisters” in Latin) explores themes of togetherness and separation, as well as balance and symmetry.
Many of the rhythmical groupings are based on the following nonretrogradable pattern:
| 4 – 5 – 6 | 7 – 8 || 8 – 7 | 6 – 5 – 4 |
The rhythmical groupings in measures 1-4 outline this pattern, with the barline between mm. 2-3 as the axis of metric symmetry. For this reason, the piece begins and ends in 15/16 time (4 + 5 + 6 + 7 + 8). 15 is also the sum of 8 + 4 + 2 + 1 — a triple dotted half note in this context.
In measures 5-8, the pattern from mm. 1-4 is repeated in pitch inversion. Here, the axis of symmetry is halfway between the middle two strings of the violin (D and A): F / F-sharp. Significantly, this is also the midpoint of the outer two strings of the violin.
The barline between mm. 4-5 serves as the temporal axis of symmetry for bars 1-8; the barline between mm. 8-9 serves as the temporal axis of symmetry for bars 1-16; etc.
These mirror effects continue throughout the piece on large and small scales.
Relations are also drawn between pitches through the use of the natural harmonic series. While the natural harmonics of an open string are created from the same fundamental, they retain unique pitch and coloristic identities; they are, as it were, sisters.
The two voices are always offset until the very end, when they finally converge.
This piece was written for Dhyani Heath and Susila Heath, who premiered it in Paris in 2022.