A lowpass gate is essentially a low pass VCF configured to behave like a VCA. The lowpass gate accepts an audio input and a control signal, in the manner of a VCA. When there is no control signal present, the filter's cutoff frequency is in the subsonic range, well below the audio frequencies; therefore, no audio passes the filter. Applying a control voltage causes the cutoff frequency to rise significantly, into the upper end of the audio range, so that most of the audio at the input now passes. If the output of an envelope generator is presented to the control input, the lowpass gate will shape the note envelope as a VCA would, but with some characteristic differences.