Subtle difference: GrandOrgue uses samples of actual organs, pipe-by-pipe. It can direct its output to many different channels and has software mixers to map the outputs onto the number of channels you've got. An 'electronic organ' is a device that creates organ-like sounds, either using tonewheels (for instance: Hammond) or some electronic oscillator and then uses various methods to mix in or filter harmonics. This can create sounds that closely approximate a real organ but it isn't quite the same because you don't have that massive soundbox called a church to go with it (I see churches as very nice instrument casings).
Moddarts 'Organteq' comes very close with their virtual organ simulator, it uses a whole pile of math to recreate the sounds of a real organ. Using that + a multi manual setup gives you a close approximation to a real organ which you can configure to your hearts content. But the software used in this project, GrandOrgue which uses samples is also very good (and is the one I use).
Playing an organ is - in my opinion - a lot harder than to play a piano, the learning curve is very steep and the added footwork is a serious complication if all you've ever done is play the piano. I suck at both ;) But it is a lot of fun.
I'm using it on Ubuntu Studio with Jack and that's fast enough that I don't see lag. It'll never be as quick as an electronic piano but midi over USB is quite fast. I love their Linux support by the way, rock solid.
Moddarts 'Organteq' comes very close with their virtual organ simulator, it uses a whole pile of math to recreate the sounds of a real organ. Using that + a multi manual setup gives you a close approximation to a real organ which you can configure to your hearts content. But the software used in this project, GrandOrgue which uses samples is also very good (and is the one I use).
Playing an organ is - in my opinion - a lot harder than to play a piano, the learning curve is very steep and the added footwork is a serious complication if all you've ever done is play the piano. I suck at both ;) But it is a lot of fun.