The digital waveguide plucked once and left to ring — a
bow drives the string continuously instead, through friction.
A real bow alternately sticks to the string (moving with it) and slips free,
over and over, every cycle — the stick-slip motion that gives a bowed tone its sawtooth-ish
buzz, unlike a pluck's cleaner decay. Too little bow pressure and the string barely catches;
too much and it turns scratchy — the same sweet spot a real string player learns by feel. Hand-written
in an AudioWorklet; the friction curve is a simplified stand-in (see
js/synth-string.js), not a literal reproduction of a published bow model.
Bow position is distance from the bridge, same idea as the waveguide's pick position — near the bridge (sul ponticello) is brighter and glassier, mid-string is warmer.
Pressure does two things at once, like a real bow: it narrows the string's "stick" window (grippier) and pushes harder (louder) — drag it up from silent-and-breathy, through clean, into scratchy.
play with your keyboard (a s d f …) or click the keys — holding a key keeps the bow moving