Task: Question Generation
Input (English): Passage: Barbirolli is remembered as an interpreter of Elgar, Vaughan Williams and Mahler, as well as Schubert, Beethoven, Sibelius, Verdi and Puccini, and as a staunch supporter of new works by British composers. Vaughan Williams dedicated his Seventh and Eighth Symphonies to Barbirolli, whose nickname, "Glorious John", comes from the inscription Vaughan Williams wrote at the head of the score of the Eighth: "For glorious John, with love and admiration from Ralph." Barbirolli did not disdain lighter repertoire. The music critic Richard Osborne wrote that, if all Barbirolli's recordings were to be lost except that of Lehár's Gold and Silver Waltz, "there would be reason enough to say, 'Now, there was a conductor!'"Barbirolli's repertoire was not as wide as that of many of his colleagues because he insisted on exhaustive preparation for any work he conducted. His colleague Sir Adrian Boult liked and admired Barbirolli but teased him for his meticulousness: "We can't all be like you and spend months studying these things and then have days of rehearsals before we conduct them. For some of us they're only sporting events." Barbirolli was shocked by such levity. His approach was illustrated by the care he took with Mahler's symphonies. His biographer Michael Kennedy commented, "it is ironical that the effort of composing the symphonies shortened Mahler's life; interpreting them certainly put an enormous strain on Barbirolli in his last decade." He found that mastering a Mahler symphony took between 18 months and two years, and he would spend hours meticulously bowing all the string parts in preparation for his performances. His first performance of Mahler's Ninth took nearly 50 hours of rehearsal.
Output (English): What is the last name of the person who found that mastering a Mahler symphony took between 18 months and two years?