Reginator wrote:1) The organist and his assistant were using what looked like a patch sheet to set up the sound.
For "patch sheet" read "Stop list" - the larger the instrument, the more sensible it is to write down the stops required for any piece, especially organs without capture systems or computerised performance aids, although St Sulpice even has one of those with its extraordinary mechanical capture system.
Btw, St Sulpice's organ sounds massive!!
Sulpice sounds fricken awesome (!) as any well built instrument should, but particularly with Cavaille-Coll who was not only an exceptional and imaginative engineer, but had a great ear for tonal finishing. So between re-defining how the organ could be built mechanically, and re-defining how pipes could be voiced, he seriously gave the instrument a powerful rebirth at the time.
wurly60 wrote:On tracker style organs like St. Sulpice, because it is all mechanical, yes you can in a way change the pitch of the rank of pipes by pulling the stop part way out which is only pulling the valve part way out restricting air to that stop.
Quite right, although if you'll excuse my pedantry, this can't actually be done at St Sulpice because of the pneumatic assistance that C-C put on each stop knob so that they could be each used in his adaptation of the Barker lever (that allowed for the aforementioned capture system). But absolutely, on a straight mechanical stop action, you can. This performance of the infamous Ligeti Volumina
demonstrates this well. About 4:25 in, you can see the registrants slowly moving stops in and out and can hear how the pipes pitches "bend" accordingly.
I've played a similar work by Jacques Charpentier, which called for stops to be pulled half-way out so that some of the clusters were microtonal.
Getting back to the "synthesis" topic there are quite a few of the better known French 20th Century composers who did some extraordinary things with registration, coaxing sounds from the organ that many seasoned (and some cynical) organists probably weren't aware of.
The most outstanding of them for my ears (and hands and feet) was Olivier Messiaen. Check out his "Chants d'Oiseaux". You'll see how often this performer changes registrations to achieve the sounds Messiaen requests in the score (it's actually quite a brave move doing this on a 2-manual ... 4 is much easier!). Even though the audio quality is not great, you'll still hear how distinctive the sounds are and how brilliantly Messiaen evokes the 4 principal bird's songs. (Messiaen greatly admired birds, gaining much inspiration from them - bird song is found in a great deal of his music).
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