The Christopher Wren-inspired Christ Church, attended by several of our nation’s founding fathers and mothers, is located in the heart of the historic district of Philadelphia, Old City. Its airy interior is graced with arched, multipane windows, an elegant barrel-vault ceiling, and handsome Palladian features that visually express the birthplace of our democracy in the ideal proportions of Greco-Roman architecture. At the center of the wrap-around gallery was a stunning white organ case whose somewhat mysterious history goes back to the original 1766 instrument by Philip Feyring and a distinguished later organ built by Henry Erben in 1837.
In December 2015, Christ Church contracted C. B. Fisk, Inc. to replace the failing electro-pneumatic instrument behind this historically significant case. In preparation for tonal design, Fisk staff members joined acoustician Dana Kirkegaard at Christ Church to engage in acoustical studies of the nave space. The listening experience involved a vocal quartet and numerous instrumentalists performing at various locations within the gallery envelope. Amused, if not petrified, at where they were asked to perch while they played or sang, the musicians used step ladders, temporary staging, even the interior walkboards of the old organ.
In the end, these tests not only made a revelation about the room’s acoustics and reverberation but also guided everyone as to divisional placement and wind pressures, revealing three aural “sweet spots”: first, a dynamic elevation for the main Great and Swell divisions approximately 12' above floor level from where the musicians’ sounds spoke clearly to the nave and engaged the entire breadth of the room; second, a vocally resonant spot 6' higher up in the space, closer to the ceiling vault, from which the live sounds “lit up” the upper volume of the nave – and where four of the Great division’s solo stops were placed; and last, a delicate, focused, and extremely beautiful place for sound at the center of the gallery railing. These studies confirmed definitively that the sound-producing portion of the new organ must reside fully in the church's gallery, not in the historic tower where much of the pipework of the old organ had been. That meant placing the organ in front of the old archway that had been between the nave and Ben Franklin's tower and filling this open archway back up to create a massive, bass-reflective wall.
Conversations with Timothy Safford and Parker Kitterman brought to light their earnest hope that we could design an organ that would feel closer to the people in the pews and better integrate the choir into the worship experience. This desire, together with the acoustical tests, plainly pointed to adding a Chaire division on the gallery rail, as well as to changing the rail into one that was more acoustically open to the instruments and voices behind it.
A design model, at 1:16 scale, helped to develop the profile, proportions, and position of the Chaire casework and to fine-tune the scaling of its cornices, carvings, and under-paneling details. The model guided everyone to many other solutions, such as lifting the Erben case about 30" on a new but formally paneled base, and was an effective tool in the close collaboration with Christopher Miller of Milner Architects, the church committees, and the Philadelphia regulatory agencies.
It has been said that the best compliment that you can give a new pipe organ in a historic room is that it looks “as if it had always been there” -- and, that it sounds that way, too. It is the hope that the nuanced, vocal voicing of Opus 150 on relatively low wind pressures (2¼" water column for the manuals) will inspire all who hear it, reinforcing the sense that this organ is uniquely suited to its home within Christ Church Philadelphia.