A house organ such as this cabinet organ is not pre-eminently an instrument that you will encounter in a Cathedral. In reality, this Onderhorst cabinet organ is now in a village church in Bennekom(the Netherlands), where it is regularly used as a concert instrument.
I made the recordings for the samples of this organ a short distance from the organ with one stereo microphone in a so-called XY setup. The aim is that the player of the virtual organ experiences the sound as if he / she is sitting on the organ stool of the real organ.
Using acoustics simulation, a dry sample set like this one can be used to simulate how the instrument sounds in a particular room. In extremo even in a Cathedral, as was done here by way of demonstration.
Acoustics simulation is not simply: “adding (convolution) reverb” and certainly not mixing reverb with the direct sound of the samples. At the stool of the organ (where the direct sound has been recorded) you will hardly hear the reverberation, even if you were to put the organ in a cathedral. To hear the organ in its acoustic environment you have to distance yourself. The direct sound then becomes softer, but also less broad, the frequency spectrum changes.
For this recording, the cabinet organ has been virtually placed in the “Notre Dame of Kispest” (Hungary), with acoustics simulation via ORIGAMI using IRs from Inspired Acoustics.
This can be done by yourself with HW4 via the VST link (the free version is sufficient), Cantabile Lite and ORIGAMI (part of Independence by Magix).