If you use the Modelica Language for simulation it's basically a rite of passage to at least try out OpenModelica, although your mileage on various operating systems and versions thereof can vary wildly (you can always ask for the money back that you didn't pay).
NEWS: SysML Extension for Physical Interaction and Signal Flow Simulation (SysPhS): New technology assessment trail: TRAIL: SysPhS-1.1 specification body figures in MagicDraw SysML (or Cameo Systems Modeler) vs Modelica
NEWS: SysML Extension for Physical Interaction and Signal Flow Simulation (SysPhS): New technology asse
In this Webel mini-tutorial trail for PureData synthesis you'll find some snapshots of patches used to create the "sound circles" animated logo for the PLAY music/art projects. Each circle (created with PureData/GEM) corresponds to an evolving oscillator frequency with evolving amplitude and pan.