Xenakis Stochastic/Sieve

Start with stochastic raw material: Random Pitches for uniformly distributed pitches across a range, or Random Walk for a melodic line that wanders organically with constrained step sizes. Set the range and quantization to match your desired ambitus and temperament.

Filter the result through a Sieve node with modular congruence conditions. For example, moduli [3, 5] with residues [0, 1] retains only pitches at indices that are either divisible by 3 or have remainder 1 when divided by 5. This produces the irregular, non-periodic pitch distributions characteristic of Xenakis's sieve-based compositions — asymmetric scales and pitch selections that sound neither tonal nor uniformly chromatic.

Optionally pass the sieved material through a Permute node with a specific index sequence to impose a particular ordering. Combine with stochastic rhythms for fully Xenakis-inspired textures, or pair with structured rhythm trees for a hybrid approach.