Tassman is an extremly rich modular sound synthesis environment based on physical modeling.
It is both an impressive collection of unique synths and effect processors, and a tightly integrated synthesis studio which lets you customize instruments in any way you wish or even create your own from scratch. It comes with a library of 50 synths and more than 1000 presets created by top sound designers. These offer a near infinite range of creative possibilities, from highly realistic emulation of acoustic instruments, analog and FM synthesizers, loop processors to unique hybrid creation simply not possible by any other means. Tassman can be used both as a synthesizer and a real-time audio effect processor. For example, acoustic resonators can be used to add unique texture to your sound. Use Tassman as an effect plug-in in your favorite host application.
more info can be found here Tassman 4