Question: Roy Galbriath Henderson taught what English contralto singer that died of cancer during the height of her career? 

full_context: Document 1: Kennerley Rumford: Robert Henry Kennerley Rumford (2 September 1870 – 9 March 1957) was an English baritone singer of the 20th century. He was first known for his performances of Oratorio, but following his marriage to the well-known contralto singer Clara Butt, he toured with her throughout the English-speaking world singing repertoire of a more popular type. He was twice mentioned in dispatches while serving on the Western Front during the First World War.
Document 2: Norma Procter: Norma Procter (15 February 1928, Cleethorpes, Lincolnshire – 2 May 2017, Grimsby) was an English contralto who studied with Roy Henderson.
Document 3: Kathleen Battle: Kathleen Deanna Battle (born August 13, 1948) is an American operatic soprano known for her distinctive vocal range and tone. Born in Portsmouth, Ohio, Battle initially became known for her work within the concert repertoire through performances with major orchestras during the early and mid-1970s. She made her opera debut in 1975. Battle expanded her repertoire into lyric soprano and coloratura soprano roles during the 1980s and early 1990s until her eventual dismissal from the Metropolitan Opera in 1994. After a 22-year absence from the Met, Battle performed a concert of spirituals at the Metropolitan Opera House in November 2016.
Document 4: Clara Butt: Dame Clara Ellen Butt, DBE (1 February 1872 – 23 January 1936) was an English contralto. Her main career was as a recitalist and concert singer. Her voice, both powerful and deep, impressed contemporary composers such as Saint-Saëns and Elgar; the latter composed a song-cycle with her in mind as soloist.
Document 5: Dietrich Fischer-Dieskau: Dietrich Fischer-Dieskau (28 May 192518 May 2012) was a German lyric baritone and conductor of classical music, one of the most famous Lieder (art song) performers of the post-war period, best known as a singer of Franz Schubert's Lieder, particularly ""Winterreise"" of which his recordings with accompanist Gerald Moore and Jörg Demus are still critically acclaimed half a century after their release.
Document 6: Anne Collins (contralto): Anne Collins (29 August 1943 – 15 July 2009) was an English contralto known as versatile operatic singer, praised for her "beautifully warm and wide-ranging timbre, and impeccable diction". In a career that spanned nearly 40 years, she sang a wide range of operatic character roles and other classical pieces, including standard opera repertory, premieres, 20th century pieces, art song and other music.
Document 7: Roy Shepherd (pianist): Roy Shepherd MBE (190720 June 1986) was an Australian pianist who is most renowned as a piano teacher at the University of Melbourne Conservatorium.
Document 8: Roy Henderson (baritone): Roy Galbraith Henderson CBE (4 July 189916 March 2000) was a leading English baritone in the 1920s, 1930s and 1940s. He later became a teacher of singing, his most notable student being Kathleen Ferrier.
Document 9: Joseph Ward (tenor): Joseph Ward OBE (born Preston, 1932) is an English tenor, formerly a baritone, who created roles in operas by Benjamin Britten and Michael Tippett. He has also made a career as a singing teacher – his pupils include Jane Eaglen – and opera producer.
Document 10: Kathleen Ferrier: Kathleen Mary Ferrier, CBE (22 April 19128 October 1953) was an English contralto singer who achieved an international reputation as a stage, concert and recording artist, with a repertoire extending from folksong and popular ballads to the classical works of Bach, Brahms, Mahler and Elgar. Her death from cancer, at the height of her fame, was a shock to the musical world and particularly to the general public, which was kept in ignorance of the nature of her illness until after her death.
Document 11: Kathleen Ferrier discography: In the course of her professional life the English contralto Kathleen Ferrier made a large number of recordings. In the summer of 1944 she signed a contract with Columbia, which lasted until February 1946. She then transferred to Decca, and remained with them until her death in October 1953. Apart from her studio recordings, many of her live performances and broadcast recitals were recorded, sometimes privately. Some of these were later issued as commercial recordings; others are held by individuals or in the archives of broadcasting companies. The list is not necessarily complete.
Document 12: Elisabeth Schwarzkopf: Dame Olga Maria Elisabeth Friederike Schwarzkopf, DBE (9 December 19153 August 2006) was a German soprano. She was among the foremost singers of lieder, and was renowned for her performances of Viennese operetta, as well as the operas of Mozart, Wagner and Richard Strauss After retiring from the stage, she was a voice teacher internationally. She is considered one of the greatest sopranos of the 20th Century.
Document 13: Eileen Farrell: Eileen Farrell (February 13, 1920 – March 23, 2002) was an American soprano who had a nearly 60-year-long career performing both classical and popular music in concerts, theatres, on radio and television, and on disc. While she was active as an opera singer, her concert engagements far outnumbered her theatrical appearances. Her career was mainly based in the United States, although she did perform internationally. "The Daily Telegraph" stated that she "was one of the finest American sopranos of the 20th century; she had a voice of magnificent proportions which she used with both acumen and artistry in a wide variety of roles." And described as having a voice "like some unparalleled phenomenon of nature. She is to singers what Niagara is to waterfalls."
Document 14: Robert Carr (baritone): Robert Carr (12 April 1881 – 20 November 1948) was an English baritone singer and prolific recording artist. Born in London, he studied at the Guildhall School of Music and Drama under Bantock Pierrepoint. He recorded under his own name and as variously Richard Condor, William Duncan, Harry Durrant, Robert Durrant, Ernest Gray, Bobby Gray, Robert Oswald, and perhaps some others.
Document 15: Nellie Melba: Dame Nellie Melba GBE (19 May 186123 February 1931), born Helen Porter Mitchell, was an Australian operatic soprano. She became one of the most famous singers of the late Victorian era and the early 20th century. She was the first Australian to achieve international recognition as a classical musician. She took the pseudonym "Melba" from Melbourne, her home town.
ground_truth: Kathleen Mary Ferrier