As said above, check out some Softsynths.
There should be demos that are free to download, even for Mac users.
Download some demos, fiddle around with their controls, (lots of knobs that you can even move with the mouse) and use an old Midi capable keyboard (if you have one) or a cheap controller, and "play" with it. Yuo shold be able to get a "feel" of what is like and if in a matter of weeks it proves to be satisfactory, amusing, pleasing etc etc, then go for the full version and maybe buy a controller with enough knobs so you can have a "Moog like" knob heaven on your desk.