The modus operandi of some generator controls is not immediately obvious. These controls are documented here.
This applies a trochoidal twist such that the coil doubles back on itself, rather like a Mobius strip. As the value moves toward
HALF_PI (90°), it creates two apparent coils - an inner and an outer - though both are formed from the single mesh. This resuls in two apertures, each facing in opposite directions. The normals of the inner aperature face inward, whilst the normals of the outer aperture face outward.
This ‘bends’ the axis of the trochoidal shift and is useful when generating horns.
Tropism A applies pitch and Tropism B applies roll.