You can watch in this video the work of left hand on the ostinato:
György Ligeti (1923–2006) was a Hungarian composer of contemporary classical music. He has been described as "one of the most important avant-garde composers in the latter half of the twentieth century" and "one of the most innovative and influential among progressive figures of his time".
Musica ricercata is a set of eleven pieces for piano by György Ligeti. The work was composed from 1951 to 1953.
Ligeti's title should probably be interpreted literally as "researched music" or "sought music". This work captures the essence of Ligeti's search to construct his own compositional style ex nihilo, and as such presages many of the more radical directions Ligeti would take in the future.
VII. Cantabile, molto legato
A most intriguing and unique movement, it begins with a seven-note ostinato in the left hand that Ligeti indicates should be rhythmically and dynamically independent from the right hand. The right hand carries a folk-like melody that is first heard alone in single notes before it gets juxtaposed in a loose canon with various transformed versions of itself, producing a lively counterpoint with rich harmonies and a sense of rhythmic freedom. Eventually, both hands move up an octave, significantly lightening the texture. The piece concludes with the right hand taking over the ostinato at a yet higher octave; the ostinato progressively loses notes until it is only a trill on F and G which proceeds to fade away to silence. This movement is clearly based on the second movement, "Andante", from the composer's Sonatina for Piano, Four Hands. It is used again in the second movement of his Violin Concerto (1992). Lo Muscio has transcribed the piece n.7 for organ in 2016.