Igor Fyodorovich Stravinsky (Russian: Игорь Ѳёдоровичъ Стравинскій) (17th June 1882 – 6th April 1971) was a Russian composer who first achieved international fame with three ballets commissioned by the impresario Serge Diaghilev and performed by Diaghilev's Ballets Russes (Russian Ballet): L'Oiseau de feu ("The Firebird") (1910), Petrushka (1911), and Le sacre du printemps ("The Rite of Spring") (1913). Stravinsky's compositional career was notable for its stylistic diversity. After his first, Russian (expressionistic), phase he turned in the 1920s to neoclassicism. The works from this period tended to make use of traditional musical forms (concerto grosso, fugue, symphony), frequently concealed a vein of intense emotion beneath a surface appearance of detachment or austerity, and often paid tribute to the music of earlier masters, for example J.S. Bach, Verdi and Tchaikovsky. In the 1950s he adopted serial procedures, using the new techniques over the final twenty years of his life to write works that were briefer and of greater rhythmic, harmonic, and textural complexity than his earlier music. Their intricacy notwithstanding, these pieces share traits with all of Stravinsky's earlier output; rhythmic energy, the construction of extended melodic ideas out of a few cells comprising only two or three notes, and clarity of form, instrumentation, and of utterance. Stravinsky only started using the twelve-tone system after the death of Schoenberg in 1951. At that time dodecaphony was a well-known and widely spread system that was generally accepted as a valuable 'replacement' of the tonal system. Therefore, some musicologists thought it wiser to consider the serial works of Stravinsky as a sort of neo-dodecaphony, meaning that they are also conceived as "neoclassical". Stravinsky achieved fame as a pianist and conductor, often at the premieres of his works. He was a writer and compiled, with the help of Alexis Roland-Manuel, a theoretical work entitled Poetics of Music, in which he famously claimed that music was incapable of "expressing anything but itself". Several interviews in which the composer spoke to Robert Craft were published as Conversations with Stravinsky. They collaborated on five further volumes over the following decade.