Syrmos

Iannis Xenakis
Syrmos for 18 strings (1959)

Orchestral composition: 6.6.0.4.2

The work is based on stochastic transformation of 8 basic textures.

horizontal parallel networks (chord)
ascendant parallel networks (glissandi)
descendant parallel networks (glissandi)
crossed parallel networks (ascendant and descendant)
clouds of pizzicati
atmosphere of frappes collegno with short glissandi col legno
configurations of glissandi traited in regulated left surfaces
geometric configurations of ascending and descending glissandi

This piece is based on a stochastic process known as a Markov chain. It is a system in which the transition from one state to another depends solely on the current situation and is governed by a table that, given the current state, specifies the probabilities of transition from that state to another.

In simpler terms, imagine that, at this moment, the orchestra is in state (e), that is, it is playing a cloud of pizzicato notes. Row (e) of the table specifies the probabilities of the orchestra transitioning to one of the states from (a) to (h), including the probability of remaining in state (e).

Obviously, the table is square because, for each possible current state, there is a row defining the probabilities of transitioning to all states, including the probability of remaining in the current state (in theory, silence should also be included among the possible states, but, in Xenakis' logic, it is usually treated as a density of sounds instead).

This organizational system can be applied both to the orchestra as a whole and to individual instruments.

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