John Jeavons asks:
"What is a ventil system? What is a Barker machine? I really appreciate hearing about your experiences on such an organ. How did you select the registration such that it would match with the choir? Did you do it beforehand in anticipation of what they want or did you get some time to work with them and choose the registrations?"
Ventils in the mechanical action organ serve at least two functions - to conserve wind and to prepare certain registration combinations in advance. If you put, say 10 stops on a separate windchest than the rest of the stops in that manual, you can prepare any combination of these 10 stops in advance and when the time comes, you simply draw the ventil out and this combination would start to sound.
Now imagine that there are 16 ventils on the organ (every manual has 2 but Haupwerk and Pedals have 5 windchests each) This means there might be 16 x 16 combinations to choose from. Huge possibilities to change dynamics and colors and very efficient on a large mechanical organ. Also when you have that many stops on one manual, having just one windchest wouldn't work - the pipes would lack air to sound so you need to separate them.
Here is an explanation of how Barker machine works. Basically under each key of a particular manual (in the case of Liepaja organ - the Hauptwerk) - there are miniature bellows which help to depress the keys on that manual. An organist doesn't have to fight the resistance of the action on a large mechanical action organ because these small bellows do the work.
When playing with or without the choir, I always prepare my registration before hand (either on paper or in my mind). This saves precious rehearsal time. For the last year's recital in Liepaja, I didn't use much of the ventils, most of the stops my assistant pulled by hand. That's a lot of work. But this year, after following the advice of Janis Kalnins, my friend and organ builder from Latvia who knows this organ inside out, I decided this time would be different. Here's what I did:
I looked at the score of the Gounod's Solemn Mass for Saint Cecilia and noticed that there are 8 different dynamic levels: ppp, pp, p, mp, mf, f, ff, and fff. Then I looked at the disposition of the organ in Liepaja and selected certain ventils to go with certain dynamic levels. This I decided after examining the nature of the stops on each manual and windchest. The same I did with the pedal windchests. Then I wrote out the stops and their combinations for each dynamic level on a specific windchest I wanted.
This was my starting registration with some of the ventils engaged. During the performance, my assistant only had to operate those ventils which are grouped together on the right hand side of the organ console (plus one coupler). As far as I could tell, it was so much easier for my assistant because everything was so close together. On the score I only wrote the numbers of the ventils and plus and minus signs.
What is interesting that I didn't have any additional personal time at the organ, we started rehearsing with the choir right away. So it's good I was prepared. And it worked for most of the ventils. Of course, a few ventils had to be adjusted (reduced or increased sound).
John Higgins asks:
"Are there any challenges around keeping timing with the choir in a resonant acoustic? I have heard that sometimes certain keys or pitches can be difficult in large cathedrals. I would imagine being mechanical action and having the pipes right in front and above you there wouldn’t be too many problems with a delay from the key being pressed to hearing the note? Also I notice the naming of the manuals and some of the stops seemed to be in the German style. Pardon my ignorance of the culture in this area, is this common that organs in Latvia (and Lithuania) would be named in the German style? Also, would it be more common for the Echowerk to be the top manual rather than the bottom manual?"
As strange as it may sound, this cathedral doesn't have a very reverberate room. Acoustics were not dry but moderate, I would say and certainly less reverberate than in our Vilnius University St. John's church. Because the organ is so large and the pipes are all over the place, there was a certain tendency to drag the tempo so I knew that in advance. Leading with the organ helps. If you are following, you are late. But if you are leading - you might be on time.
The reason the stop names and manual names are German is that this organ was built by the Curonian organ builder Heinrich Andreas Contius and enlarged by Barnim Grunewald from Stettin and because this Curonian area was German influenced culturally. In Lithuania, we have more Italianate names of organ terms. Perhaps because this is mostly Catholic country whereas Latvia is predominantly Lutheran.
Concerning position of the Echowerk - yes, it seemed strange to me that it is the lowest manual and not the top as usual. I had to adjust my expectations with manual jumps as well.
Anyway, I hope this helps to clarify the questions people might have about this organ and my experience in playing it.