Complex sentence: Sergei Sergeyevich Prokofiev (;; 23 April 1891--5 March 1953) was a Russian composer, pianist and conductor who mastered numerous musical genres and is regarded as one of the major composers of the 20th century.
Split into simpler sentences: Sergei Sergeyevich Prokofiev (;; 23 April 1891--5 March 1953) was a Russian composer, pianist and conductor. As the creator of acknowledged masterpieces across numerous musical genres, he is regarded as one of the major composers of the 20th century.