In 1955, while in the midst of working on a musical version of Voltaire's Candide with the distinguished American playwright Lillian Hellman, Leonard Bernstein composed French and Latin choruses as incidental music to the play The Lark adapted by Miss Hellman from the original French version by Jean Anouilh. Since the drama was about the trial of Joan of Arc, Bernstein’s music was deliberately evocative of the medieval era. In fact, the music was performed (on tape) by seven members of the New York Pro Musica Antiqua, a group specialising in pre-17th century music. Robert Shaw attended one of the first performances and suggested to Leonard Bernstein that with some changes and additions the music would make an effective Missa Brevis. Thirty-three years later, in honour of Maestro Shaw's retirement as Music Director of the Atlanta Symphony Orchestra, Bernstein has followed his colleague's suggestions.