curveccN
The curvecc modifier, when it’s present, designates a ‹curve› which shapes
the controller input. If absent, the default curve is used, a straight line
which runs from 0 to 1.
The value of curvecc is a positive integer. It is the index of a curve,
either built in or user-defined, which corresponds to the ‹curve› opcode
curve_index.