Sonido 13 is a theory of microtonal music created by the Mexican composer Julián Carrillo around 1900[1] and described by Nicolas Slonimsky as "the field of sounds smaller than the twelve semitones of the tempered scale.
Julián Carrillo wrote: "The thirteenth sound will be the beginning of the end and the point of departure of a new musical generation which will transform everything.
"[5][6] Carrillo attended the National Conservatory of Music in Mexico City, where he studied violin, composition, physics, acoustics, and mathematics.
One day, Carrillo was able to divide the fourth string of his violin with a razor into 16 parts in the interval between the notes G and A, thus creating 16 unique sounds.
His achievements in this area were extensive and consisted of writing over 20 books, making more than 40 compositions, patenting fifteen pianos capable of producing small intervals, and organizing the Sonido 13 Symphonic Orchestra that performed in different parts of the world, playing microtonal music composed by Carrillo in different intervals.