『Aristide Cavaille-Coll, part II』from the column【My First Sound】 by Justin Berg, the Executive Director of Orgelkids China. (In English below)
〜Cavaille-Coll (Part II)--3
However, there are other features of this specification that depart from Classical designs. Among these, note the relative lack of mutation stops in the Grand-Orgue and Récit, especially third-sounding ranks such as the Tierce. Furthermore, there is a wealth of 8’foundation stops that were not found even in later 18th century instruments. Perhaps the most compelling evidence of innovation, though, can be seen in the Récit: extended to full compass and placed under expression — a French Swell box! Small Swell divisions were already known in England by the later 18th century, but they generally did not enclose a full-compass division, nor did they enclose so many stops. In fact, the size of the Récit at St. Denis already hints at the importance this division would assume in later Cavaille-Coll instruments. Also, the pedal that controlled the Swell shutters was redesigned with a spring which gave the organist the ability to gradually and smoothly open and close the Swell, rather than simply having it completely open or closed.
Underlying these obvious changes to the Classical organ were technical innovations that substantially altered the sound of Cavaille-Coll’s instruments. Perhaps most celebrated of these inventions was the Barker Machine, mentioned above, which allowed most of an organ’s stops to be played together with a relatively light touch. Since it is not easy to understand the concept of a Barker Machine without an Engineering degree, we can try to think of a practical comparison. Imagine that you sit down to play a giant pipe organ. You pull out most of the stops, wanting to play loudly, but when you try to depress the keys, they barely move. This is because there is so much wind pressure and resistance from the complicated action that connects the keys to the pipes.
That was precisely the problem that Cavaille-Coll encountered. His solution was to insert Barker’s invention — a kind of small box — between the keys and the rods (trackers) that connected them to the pipes. When the organist depressed a key, this box (one per key) filled with air and the pressure from that air pushed the remaining connecting rods, finally opening the small door (or pallet) under each pipe. This is the basic idea of the Barker Machine. Pushing down the keys on such an organ is a little like pressing on a marshmallow: while you press down on one end, the other end bulges, and that outward bulge helps move the other parts that open the pallet and admit wind to the pipes. While this is a very basic, and therefore somewhat misleading comparison, it gives you a general idea of Barker’s invention.
The ingenuity of the Barker Machine helps explain one of the most interesting aspects of the St. Denis organ: the Grand-Orgue and Bombarde divisions both play from a single keyboard. This means, that even though there are four manual divisions, there are only three keyboards. Having a pneumatic assist (i.e. Barker Machine) was the only way to comfortably play such an enormous chorus of stops on a single keyboard. When combined, the Grand-Orgue and Bombarde in full chorus includes the principals from 32’ Montre through the four mixtures (Fourniture and Cymbale), as well as a 16’ Bombarde, four 8’ Trompette’, and three 4’ Clairon — a true battery of reeds! All of this demands a great deal of wind. And of course, these could be coupled to other divisions, with their own reedwork, which brings us to one final, striking feature of Cavaille-Coll’s design: in addition to the various standard manual and pedal couplers, there are also suboctave couplers, which allow
manuals to be coupled at 16’ pitch. This innovation not only permits a more ponderous, serious tone, but also contributes to the weight of the key action and therefore the need for the Barker Machine.
Though there is more that we could explore in this grand instrument, it is time now to leave and let the inspiration of its design settle into our imaginations. Next time, in the third and final installment of this article on Cavaille-Coll, we will turn our attention to later developments in his style by considering two widely contrasting instruments: his small Choir organs, and one of his final, yet unrealized projects: the mammoth organ he designed for St. Peter’s Basilica in Rome.