Analog Box, a free Windows app from Andyware, is a low level, circuit based, modular software synthesizer. You put sound objects on the screen, connect them together, listen and adjust. When you find something you like, you can record it to a wav file, or just save the circuit and play it again later.
ABox is somewhat like the vintage synth’s of the ’70’s in that there are separate modules with lots of patch cords, knobs, buttons and displays. But you also get the computational ability offered by modern CPU’s. Features like FFTs, Differentials and Digital Control open up realms of sound design.
Get objects from the palette, put them where you want, connect them however you like. Adjust parameters using one click popup panels then move on.
Warning: Analog Box is the softsynth most feared by domestic pets.