
Listen to music from the period played on Italian organs of the period and get a feel for how it is meant to sound. And then experiment and find out what sounds good to you! I've just finished recording a set of pieces by Turin cathedral organist Giuseppe Cerruti (1803-69), written for just this kind of organ and played on the Sonus Paradisi Serassi at Piacenza. Below is the link to the playlist. Note that the two pieces in the first video -- the Introduzione and verset 1 -- are quite different from the other eight, which are much more typical. I give the registrations at the end of each video. I haven't quite followed the registrations suggested by Cerruti himself (the original score is also in the videos) -- I wasn't sure I always understood quite what he meant, and he presumably intended these registrations for a one-manual instrument. Two-manual organs such as the one sampled by SP were rather unusual in Italy at the time, though Cerruti likely had one at Turin cathedral too.
https://www.youtube.com/playlist?list=P ... FzWfOfY3AG