Task: Question Answering
Input (English): Passage: Elgar is probably best known for the first of the five Pomp and Circumstance Marches, which were composed between 1901 and 1930. It is familiar to millions of television viewers all over the world every year who watch the Last Night of the Proms, where it is traditionally performed. When the theme of the slower middle section (technically called the "trio") of the first march came into his head, he told his friend Dora Penny, "I've got a tune that will knock 'em – will knock 'em flat". When the first march was played in 1901 at a London Promenade Concert, it was conducted by Henry J. Wood, who later wrote that the audience "rose and yelled ... the one and only time in the history of the Promenade concerts that an orchestral item was accorded a double encore." To mark the coronation of Edward VII, Elgar was commissioned to set A. C. Benson's Coronation Ode for a gala concert at the Royal Opera House in June 1901. The approval of the king was confirmed, and Elgar began work. The contralto Clara Butt had persuaded him that the trio of the first Pomp and Circumstance march could have words fitted to it, and Elgar invited Benson to do so. Elgar incorporated the new vocal version into the Ode. The publishers of the score recognised the potential of the vocal piece, "Land of Hope and Glory", and asked Benson and Elgar to make a further revision for publication as a separate song. It was immensely popular and is now considered an unofficial British national anthem. In the United States, the trio, known simply as "Pomp and Circumstance" or "The Graduation March", has been adopted since 1905 for virtually all high school and university graduations.In March 1904 a three-day festival of Elgar's works was presented at Covent Garden, an honour never before given to any English composer. The Times commented, "Four or five years ago if any one had predicted that the Opera-house would be full from floor to ceiling for the performance of an oratorio by an English composer he would probably have been supposed to be out of his mind." The king and queen attended the first concert, at which Richter conducted The Dream of Gerontius, and returned the next evening for the second, the London premiere of The Apostles (first heard the previous year at the Birmingham Festival). The final concert of the festival, conducted by Elgar, was primarily orchestral, apart for an excerpt from Caractacus and the complete Sea Pictures (sung by Clara Butt). The orchestral items were Froissart, the Enigma Variations, Cockaigne, the first two (at that time the only two) Pomp and Circumstance marches, and the premiere of a new orchestral work, In the South, inspired by a holiday in Italy. 
Question: What is the last name of the person Clara Butt persuaded that the trio of the first Pomp and Circumstance march could have words fitted to it?
Output (English): Elgar.