Orchestration
The musical forces are divided into three groups that alternate and interact with each other throughout the piece, finally fully combining at the end of the last movement. The soprano soloist and choir are accompanied by the full orchestra, the baritone and tenor soloists are accompanied by the chamber orchestra, and the boys' choir is accompanied by a small positive organ (this last group ideally being situated at some distance from the full orchestra). This group produces a very strange, distant sound. The soprano and choir and the boys' choir sing the traditional Latin Requiem text, while the tenor and baritone sing poems by Wilfred Owen, interspersed throughout.
The full orchestra consists of three flutes (third doubling piccolo), three oboes, English horn, three clarinets (third doubling E-flat clarinet and bass clarinet), two bassoons and contrabassoon, six horns, four trumpets in C, three trombones, tuba, timpani, percussion (four players: two antique cymbals (C & F#), glockenspiel, gong, bells (C & F#), vibraphone, cymbals, triangle, castanets, Chinese blocks, whip, bass drum, two side drums, tambourine, and tenor drum), piano, portable organ or harmonium (a grand organ is called for only in the Libera Me, the last movement), and strings.
The chamber orchestra consists of flute (doubling piccolo), oboe (doubling English horn), clarinet (in B flat and A), bassoon, horn, percussion (timpani, gong, cymbals, bass drum, and side drum), harp, two violins, viola, violoncello, double bass.
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