gong + kempul slendro, piano,
slentem pelog, vibraphone,
& bonang panerus slendro
Gatra is a composition by Jay Afrisando using a combination of non-deterministic L-System (a formal grammar, one of the algorithmic methods) and the human touch (from the composer). The L-System was developed by Aristid Lindenmayer and firstly used by botanists and computer scientists to mathematically model growth processes of living organisms.
Gatra, in Javanese language, means embryo or, in the Karawitan music, the smallest and flexible musical unit. The music is composed by developing 'an embryo' into certain shapes through a set of production rules or rewriting rules. The non-deterministic factor results different products in each developed musical 'embryo'. Because of this procedure, the product of L-System creates fractal, the condition which a larger entity (a larger musical unit) resembles a smaller entity (a smaller musical unit) and vice versa, although it does not always appear as a same-similarity. This fractal phenomenon also happens in a relationship of gatra (a smaller musical unit) and gendhing (a larger musical unit) in Karawitan music.
Performed by Ensemble Kyai Fatahillah at the October Meeting 2016, Yogyakarta, ID on October 15, 2016. Listen all the performed pieces here.