Hard-coding the kick/bass/backbeat while making ornaments probabilistic gives a pattern both stability and life

The fixed-skeleton-plus-flickering-ornaments design pattern splits a generative pattern into two tiers: hard-code the structural spine (kick, bass, backbeat) so the groove is always reliable, and make only the ornaments — hats, ghosts, fills, and melodic decorations — probabilistic. The fixed spine guarantees the pattern never falls apart, while the probabilistic ornaments supply life and variation. It is the safest way to make a pattern generative in performance, because the parts a listener relies on can never randomly drop out.

Examples

// fixed bd/sn spine + probabilistic hats: s(“bd sn”).stack(s(“hh*8”).degradeBy(0.3))

Assessment

In the fixed-skeleton design pattern, which parts are hard-coded and which are made probabilistic, and why does this give both stability and life?