Virtual Software Synthesizers

I would like to develop software synthesizers like the ones made by Native Instruments, etc., but I have no idea where to learn the theory and programming necessary.

Does anyone have any advice, or can anyone point me in the right direction?

Thanks,

Have you tried synthedit?

http://www.synthedit.com/

The actual engineering involves a lot of physics and calculus. There are some degree programs in synthesizer engineering. Northeastern University I believe has one, I'm sure there's many others. I mention Northeastern because I once thought about subjecting myself to such educational riff raff, I decided I'd rather work on my chops instead :-)