It is software (grandorgue) that pretends to be a pipe organ (the instrument). In order to run fast enough it needs to load every sound sample into memory to play, as well as usually multiple kinds of sound endings. I play professionally on a "small to mid sized" pipe organ with 1,438 pipes. The one I load for use at home has more than that!
The instrument was from the 1960s and I rebuilt it with a pi pico that you can see here, and you can hear the before (analog sound cards) versus one of the organs I've loaded into it here.
Hahaha yeah…it’s in many ways unfortunate that if you want to play/enjoy this instrument churches are the only option most of the time :/
Definitely worth the watts though!