Bela Bartok, Hungarian composer, died yesterday morning at the West Side Hospital after a long illness at the age of 64. One of the most important composers of modern music, he was also an outstanding specialist in musical folklore and a teacher of wide repute. He was a leading spirit of the "revolutionary" generation of musicians born in the early Eighties and ranked as the chief and most representative Hungarian composer of his epoch. Bartok was born March 25, 1881, at Nagyszentmiklos, in the Hungarian district of Torontal, now in Yugoslavia. His father was director of the school of agriculture in that community and his mother a schoolteacher. When his father died, Bartok, who was 8 at the time, already had begun to compose. His mother gave him his first piano lessons and his progress was so rapid that at 10 he made his initial public appearance as composer-pianist. From 1893 to 1899 he was in Pressburg, where he studied piano and composition with Lazlo-Erkel and Janos Batkai and wrote a number of unpublished works influenced by Brahms. In 1899 Bartok entered the Royal Academy of Music in Budapest, remaining there until 1903 as a pupil of Janos Koessler in composition and Istvan Thoman in piano. While at the academy he came under the spell of the music of Liszt, Wagner and Richard Strauss, but his "Kossuth" symphony, written the year he left the school, was Hungarian in essence. Collected Folk Music Bartok, in cooperation with Zoltan Kodaly, began collecting Hungarian folk music soon after he left the Academy. Their first joint publication, "Hungarian Folk Songs for Voice and Piano," appearing in 1906, being followed by Bartok's own "Twenty Songs" and "Szekely Ballads." His researches were extended to the folk music of Slovakian, Rumanian and Turkish language groups, both as collector and as a serious scientific investigator. In all he gathered more than 6,000 folk songs of Magyar, Slovak, Rumanian and Transylvanian origin and later, in 1913, brought back 200 Arab melodies from a visit to Biskra, Algeria. The researches in the field of the indigenous music of his people not only resulted in his volume "Hungarian Folk Music," the standard work on the subject, but also permanently influenced his creative output. In 1907 Bartok was made Professor of Piano at the Royal Academy of Music in Budapest and in 1911 he and Kodaly founded the New Hungarian Music Society. But his talents as composer were not recognized in Hungary until the performance in Budapest of his ballet, "The Wooden Prince," and his opera, "Prince Bluebeard's Castle," in 1917, and the premiere there of his Second string quartet the next year. Influenced by Debussy Shortly after his appointment to the academy he met Debussy, and as a result of this contact became more radical in his compositions. From then on he abandoned romanticism and became one of the first to write in the "neo-classic" manner. Simultaneously, he began to use the ancient scales he discovered in Hungarian folk music, and in so doing found himself bringing new harmonies into existence that led to his adoption of a twelve-tone scale capable of all sorts of new harmonic combinations, but he never became an atonalist. Bartok came to the United States for the first time in December, 1927. He made his American debut, Dec. 22, 1927, with the Philharmonic Orchestra, under Willem Mengelberg, in Carnegie Hall, when he was heard as soloist in his own "Rhapsodie," Op. 1, instead of his First piano concerto originally scheduled. The latter work received its American premiere with the composer as soloist at a concert of the Cincinnati Symphony, under Fritz Reiner, in the same hall in February, 1928, and that same month Bartok was heard with his compatriot Joseph Szigeti, the violinist, in a concert devoted largely to his own compositions presented by the Pro-Musica Society at the Gallo Theatre. Later that year he returned to Hungary. Appeared Here With Wife A concerto for violin and clarinet, written in Hungary by Bartok for Mr. Szigeti and Benny Goodman, was heard for the first time with those two artists as soloists in 1939 in Carnegie Hall. The next year Bartok returned to this country and made his first appearance in Washington, D.C., at a concert in the Congressional Library featuring the American premiere of his "Rhapsody," No. 1, for violin and piano. He participated in a program given in his honor by the League of Composers at the Museum of Modern Art, April 24, 1940. Shortly thereafter he went to Europe, returning to New York in October, 1940, with his wife Ditta Pasztory Bartok, with whom he was heard in the world premiere of his "Music for Two Pianos and Percussion," in Town Hall on Nov. 3 of that year. Later in the month the two artists gave a two-piano recital in the same auditorium. It was also in November, 1940, that Columbia University conferred the degree of Doctor of Music upon the composer and commissioned him to transcribe the vast Millman Parry collection of Yugoslav folk music recordings. Bartok was a prolific composer. His stage works, which suffered from unfortunate librettos, but contain some of his finest music, comprised the one-act opera, "Prince Bluebeard's Castle," and two mime-ballets, "The Wooden Prince" and "The Miraculous Mandarin." For orchestra he wrote two Suites, a "Dance Suite," two sets of "Hungarian Folk Songs," "Two Portraits," "Two Pictures" and other works, as well as the "Music for Strings, Percussion and Celesta," for small orchestra. His chamber music comprised six string quartets and several unpublished works. He also composed a large amount of piano music and wrote a large number of songs, many based on Hungarian folk melodies, and choral works. Some 450 songs from his collections were published, as well as his two books. From 1940 until his death Bartok lived in New York. He added several extensive works to his long list of compositions, including a violin sonata composed last winter for Yehudi Menuhin and not yet played. Bartok made his last appearance before the public Jan. 21 and 22, 1943, when he and his wife were the soloists in a new orchestral arrangement of the "Music for Two Pianos and Percussion" as a concerto. According to As Ember, New York Hungarian newspaper, the American Control Commission in Hungary recently notified the Foreign Minister that it had given permission to Bartok to return to Budapest. Bartok recently was elected a member of the Hungarian Parliament. Besides his widow, he leaves two sons, Bela and Peter. A funeral service will be held tomorrow at 2 P.M. at Universal Chapel, Lexington Avenue and Fifty-second Street. Burial will be in Ferncliff Cemetery, Hartsdale, N.Y.