Since I employ sixteen separate discrete outputs from soundcards
to power sixteen discrete speaker systems maximized to the sound
they replicate (reed cabinet /speaker designs differ from flue cabinets)
and some are biamped further - I do not use stereo pairs, but pan hard
left and right to keep each rank separate from others.

Some speaker cabs may be adjacent to each other or across the room,
but their placement and positioning to speak into the ambient atmosphere
determines their sound rather than overuse of electronic reverb.

My current experimentation is with a 20 output soundcard arrangement
to spread the assignment yet further tha n just sixteen outputs.

Since I do not have a separate output for each and every rank, lacking that,
I apportion some shared sound card assignments to avoid crowded polyphony,
sharing the ranks with a larger demand, such as [ Flute/Bour/Pic /12/Tierce]
with a rank that calls for less, such as [cathedral chime] or [vibes] stop.

Hundreds of speakers in dozens of cabinets, when well positioned, is nice!

PK
StentorVox.com

jeuxorgel wrote

... About multiple output channels: I guess this can be done simply by directing the output of one instance of FS towards a different soundcard or output from a multiple channel card.

The issue of multiple channels can not be seen apart from the reverb issue. I must say, that having the direct sound to the speakers directly in front of you, and the reverberated sound to speakers behind you, can already give a very satisfactory result.
This is also nearly the way some virutal organs do it, be-it that they use the original reverberated sound in the back of the church for this, and in fact play the double amount of wave samples which is not good for your RAM and polyphony......!!

The nice thing is, that we can precisely adjust the volumes to fit our needs.

Greetings,