Task: Question Answering
Input (English): Passage: On his release, Tippett returned to his duties at Morley, where he boosted the college's Purcell tradition by persuading Alfred Deller, the countertenor, to sing several Purcell odes at a  concert on 21 October 1944—the first modern use of a countertenor  in Purcell's music. Tippett formed a fruitful musical friendship with Benjamin Britten and Peter Pears, for whom he wrote the cantata Boyhood's End for tenor and piano. Encouraged by Britten, Tippett made arrangements for the first performance of A Child of Our Time, at London's Adelphi Theatre on 19 March 1944. Goehr conducted the London Philharmonic Orchestra, and Morley's choral forces were augmented by the London Regional Civil Defence Choir. Pears sang the tenor solo part, and other soloists were borrowed from Sadler's Wells Opera. The work was well received by critics and the public, and eventually became one of the most frequently performed large-scale choral works of the post-Second World War period, in Britain and overseas. Tippett's immediate reward was a commission from the BBC for a motet, The Weeping Babe, which became his first broadcast work when it was aired on 24 December 1944. He also began to give regular radio talks on music.In 1946 Tippett organised at Morley the first British performance of Monteverdi's Vespers, adding his own organ Preludio for the occasion. Tippett's compositions in the immediate postwar years included his  First Symphony, performed under Sargent in November 1945, and the String Quartet No. 3, premiered in October 1946 by the Zorian Quartet. His main creative energies were increasingly devoted to his first major opera, The Midsummer Marriage. During the six years from 1946 he composed almost no other music, apart from the Birthday Suite for Prince Charles (1948). 
Question: What is the name of the person whose own organ Preludio was added to the first British performance of Monteverdi's Vespers?
Output (English): Tippett.