The organ’s pipe scalings, pipe metal alloys and surface treatments, pipe constructions, and voicing techniques all follow historic precedents. The hammered lead chorus pipework of the Great division, scaled and voiced after eighteenth-century German examples, exhibits strength, gravity, and cohesiveness—all qualities that enable it to serve well in leading congregational singing. In contrast, the chorus work of the Choir division is built of hammered tin and is modeled after the flue choruses of the 1734 Louis-Alexandre Clicquot instrument in the church of St.-Jacques et St.-Christophe, Houdan (a small village outside Paris). This organ, on our February 2009 itinerary, impresses the listener with its colorful, silvery, and transparent flue choruses. At Mr. Outen’s urging, we decided to re-create these sounds—which Charles Fisk once called “a blaze of weightless color and light”—on the Choir division of Opus 136. The resulting chorus stands by itself as a lovely example of a classical French Plein jeu; in addition, it provides a spirited aural crown to the weightier Great chorus.
Noteworthy examples of French Romantic organ building included in Opus 136 are the three hammered tin string voices—the Great Salicional 8′, the Swell Viole de gambe 8′, and the Swell Voix céleste 8’—all scaled and voiced after the strings of nineteenth-century Parisian organ builder Aristide Cavaillé-Coll. The pipe bodies are overlength with tuning slots à pavillon in the French style, and the pipe mouths are fitted with Cavaillé-Coll’s singular harmonic bridges, or freins harmoniques, all of which contribute to the pipes’ characteristically rich, edgy timbre. This instrument is also home to a quartet of Cavaillé-Coll inspired harmonic flutes. Due to their double-length construction, these flutes are voiced to sound their first, or octave, harmonic (thus the term harmonic flute); this results in a very pure, slightly breathy tone with potential for great power in the treble range. The large-scaled Flûte harmonique 8′ in the Great division, singing and voluptuous in tone, takes full advantage of this potential as the instrument’s primary solo flute. The Swell Flûte traversière 8′, of moderate scale, is voiced to be imitative of an orchestral traverse flute. Together with the Swell Flûte octaviante 4′ and Octavin 2′, it forms a chorus of harmonic flutes, all under expression—an indispensable combination for nineteenth- and twentieth-century French repertoire, and ideal for choral accompaniment. All told, the Great, Choir, and Swell divisions contain nine 8′ flue stops of widely varying timbres. When drawn together, they form what the French refer to as the fonds d’huit, or 8’ foundations, a sonority of magnificent opulence and depth.