Benjamin Britten: The Burning Fiery Furnace
Humphrey Carpenter describes Britten's use of the alto in his parable for church performance thus:
Melodrak, the heathen image raised up by the Babylonians, is musically characterised by glissandi, which sounds especially gross because Britten has added, to the instruments used in Curlew River, an alto trombone representing the 'sackbut' mentioned in the biblical text. It slides about the notes grotesquely in the Melodrak music and also emphasises the pomposity of the 'Empire' passages.1
Example A.1.1: Britten, The Burning Fiery Furnace, alto trombone extracts, Faber2
In the following correspondence, Britten discusses with Roger Brenner (the trombonist who was to première the work) the glissandi, pedal tones, and other facets of the work that the composer was in the process of developing.