Decibels

log(x) is a natural logarithm, and it exists mainly so a preset can reach a decibel scale — audio level is perceptually logarithmic, and the raw bands are not. There is deliberately no log10, so convert with ln(10):

20 * log(x) / 2.302585                 # x as decibels (2.302585 is ln(10))

Worked against a real measurement: a typical band level is around 0.03, and log(0.03) is -3.5066, so that expression gives -30.5 dB. Silence is the edge to respect — log(0) is -inf, and silence produces it every time the music stops — so floor the input rather than the output:

20 * log(max(bass, 0.0001)) / 2.302585  # floored at -80 dB instead of -inf

log follows sqrt’s posture exactly: mathematically honest at the edges (log(0) = -inf, log(-1) = NaN), with max and select as the guards.

What the engine does if you don’t floor it. A non-finite value reaching a parameter snaps rather than easing: if that parameter is listed in [smoothing], the smoother passes the value straight through and keeps no state for that frame, so the binding tracks the input again as soon as it is finite. It used to be worse — the value poisoned the smoother permanently, and the binding stayed dead until you switched presets — which is why flooring the input is still the right thing to write. The guard is a floor under the failure, not a reason to skip yours: a -inf still reaches the scene for as long as the input is silent, and what that looks like is the scene’s business.

This does not reach the spectrum scene’s own element levels. An expression only sees what the grammar exposes, and those levels are scene state computed after every binding has been evaluated. To shape them, use that scene’s curve parameter instead (see Systems); log is for shaping a value you can already name.