Reports have emerged this week that Alan Doggett was dismissed as music master at Colet Court, the junior division of elite St Paul's School in Barnes, south west London, after allegations that he had abused a pupil in 1968.
He is said to have become a member of the Paedophile Information Exchange (PIE) before killing himself when he was charged with sex abuse against another boy in 1978, ten years after leaving the prep school.
Recent controversy surrounding PIE - which campaigned in the 1970s to lower the age of consent to as low as 10 - has seen former Labour cabinet minister Patricia Hewitt apologise for her links with the group.
Lord Lloyd-Webber and Sir Tim said in a statement: "Alan Doggett was the music master at Westminster Under School, where he taught Andrew's younger brother Julian. He became a friend of the Lloyd Webber family when Andrew was 12.
"Doggett asked Andrew in 1967 whether he and Tim would write an end of term concert piece for the preparatory school Colet Court. The consequence was 'Joseph and the Amazing Technicolor Dreamcoat'.
"Doggett had a track record of success with schools music. His choir had recorded previously the Daniel Jazz and the Jonah Man Jazz which were considered successes in the schools music field in the mid 1960s.
"At the time of his death we had not seen him for some time. His suicide in 1978 and the fresh allegations that were made around that time came as a complete shock to us.
"Neither of us had ever heard of the Paedophile Information Exchange until very recently and obviously had no idea that Alan Doggett was connected with it or that he could be a danger to children."