Sat Jun 23, 2018 6:57 am
Not only is recording mixture pipes separately logistically difficult, requiring access to the organ loft and a way of silencing the pipes, it may not yield satisfactory results. Mixtures simply sound different recorded separately and then reassembled. One could speculate as to the reasons - there are probably several subtle effects in each stage of recording, sample preparation and HW replay that combine to make the difference. Sounding different does not necessarily mean sounding worse, but it does mean that you risk losing the character and balance of the original ranks.
Some sample sets, particularly composites such as some of those offered by Silver Octopus, do use separable mixture ranks which can be individually tuned pipe-by-pipe, note-by-note, which might be desirable for church installations. For most sample sets, though, the only option for out-of-tune mixtures is to choose a sample from better-tuned neighbouring note, duplicate and repitch it. Since this particular set is unencrypted it is certainly technically doable yourself if you are seriously distressed by it.
I have this Casavant myself and am very pleased with it. I have not been worried by the mixture tuning, although now you have drawn my attention to it I can hear a bit of "character" in the Fourniture. Maybe not a bad thing, IMHO. If there is a criticism of this set it might be that it does rather lack character and I would worry that perfect tuning might make it even more bland. Perhaps Jiri and the beta-testers made the same call.