A lowpass gate using a slew limiter envelope and a 6dB/oct filter.

Also includes the slew output from the height control.

Input	Description
unit input	Input signal.
gate	Gate input, start rising.
height	Control how high the envelope goes.
rise	Rise time. How long does it take for the envelope to fully open.
fall	Fall time. How long after fully risen does it take for the envelope to close.