The Quilcom Subtractor is a free VST synthesizer instrument which is the result of experimentation with the idea of making a synth using only noise as a source.
There are 3 identical generators. Each one has 4 noise sources which can be mixed as required. Apart from white noise there are 3 sources based on sample and hold systems. The S&H systems provide a pseudo pitch quality as the spectrum is influenced by the MIDI pitch playing.
The pitch envelope controls the S&H noise “pitch” and also the zero-crossing S&H noise (P-env ZX). The mixed noise is then modified by a graphic envelope and a state variable filter with its own graphic envelope. All 3 envelopes can be velocity sensitive. The ratio to base pitch can also be entered.
The volume to key pitch relationship can be set for high notes louder or low notes louder. Finally, each generator’s level and pan can be adjusted.
Note that for the graphic envelopes just right-click to set options and you can zoom in by dragging up/down on the scroll bar below the envelope graph.
At the bottom of the front panel is a bunch of effects connected in series and each can be enabled or disabled.