A theremin is extremely easy to emulate using a simple sine wave. Link the amplitude to pitch and then perform it with some sort of controller (I link them to cc#2 and use a wind controller, but that\'s my controller of choice).
If you want the horror theremin sound, simply assign an lfo to manipulate the pitch.
I\'m sure that Donnie and Sean will be putting out the comprehensive theremin library with every possible variation spanning 15 CD (or 3 DVDs may the case be), but my approach will most likely give you better results
(my apologies to Donnie and Sean for this truly sarcastic commentary)