orchestra, Carrillo introduced Mexico to the music of Bach, Mozart, Beethoven, Weber, Wagner, Tchaikovsky, Rimsky-Korsakoff, Richard Strauss, Saint-Saëns, Debussy and Ravel. He directed two Beethoven Festivals in 1920 and 1921. He also introduced Mexican composers Manuel M. Ponce, Antonio Gómezanda, Juan León Mariscal, and himself, among others. In 1920, Julián Carrillo described his Thirteenth Sound Theory through the Mexican press and in conferences. It stated that, given the evolution of the musical system, the next step of musical composition must be the use of intervals smaller than half tones. He cited examples from his earlier experiments. The Thirteenth Sound Theory was not well received. Some enthusiastic people (most of them Carrillo's students) supported it, but others attacked it and its author. They said it was impossible to perceive such little intervals but, even if possible, Carrillo had stolen the idea from European musicians. The main opponent was "Group 9", consisting of seven musicians, a physician, and a lawyer. Carrillo's followers organized themselves as "Group 13". The two groups confronted each other to defend their positions through press, broadcasts and conferences. This debate is known as the Thirteenth Sound Polemic and was supported principally by the Mexico City's daily El Universal. The polemic culminated with a concert by the Group 13 on February 15, 1925. The program included several compositions of Carillo and his students in quarter-, eighth- and sixteenth-tones, performed with adapted instruments and specially trained voices. From September to November 1925, Carrillo made a Thirteenth Sound excursion through several cities of the country. In December 1925, Carrillo presented the Thirteenth Sound in Havana. In 1926 he arrived in New York City. There, he edited a few issues of the bilingual musical magazine The Thirteenth Sound: The Herald of America's Musical Culture. The League of Composers commissioned a microtonal work. He wrote the Sonata casi fantasía in quarter-, eighth- and sixteenth-tones. It was performed for the first time in Town Hall on March 13, 1926. Then, Leopold Stokowski commissioned a Carrillo work, the Concertino in quarter-, eighth- and sixteenth-tones, which Stokowski and the Philadelphia Symphony Orchestra performed in New York and Philadelphia. At that time, Carrillo wrote Leyes de Metamórfosis Musicales (Musical Metamorphosis Laws), a method to transform the tonal proportions of a work. For example, half tones become whole tones and whole tones become double tones; or half tones become quarter tones and quarters become eighths, and so on.