PhyMod works by physical modelling synthesis. It is a more complicated version of the waveguide synthesis found in the Yamaha SondiusXG. Rendering can be in realtime through DSP hardware, but there is also an off-line renderer for those without the hardware or for rendering more complex models. A sound is built up by placing elementary masses, feathers and dampers and setting their parameters. Their interaction can even be viewed in an on-screen 3D preview. Once a sound has been designed it can be triggered off using the mouse or using the microphone input (ie to create effects). PhyMod isn't really any good at creating real instruments (though it is theoretically possible, if very difficult, to create extremely realistic simulations), nor is it good at creating traditional synthesizer sounds. What is can do is create completely new types of sounds not possible with other types of synthesis.
A freely downloadable only allows a limited number of masses and links and pops up with a message every few minutes. Registration costs $35 and lifts these limitations. The DSP hardware cannot be purchased but must be built according to an article that was published in ct, a German computer magazine, in Summer 1996.