Okho

Okho is a composition for three percussionists by Iannis Xenakis completed in 1989.

Okho is a composition for three percussionists by Iannis Xenakis completed in 1989. The piece is cast in one movement and there are no explicit section markings anywhere in the score. However, it has many tempo changes and some scholars agree that, in formal terms, the piece can be divided into five parts. The first part is a canon between the three musicians, marked "♪ = 120 environ". It uses a rhythmic pattern that Xenakis called "Tititi tata" in his sketches. However, from bar 13 onwards, the development process was automated using a program Xenakis developed throughout his career to build his musical language called GENDY (GEN for "generation" and DY for "dynamic") or GENDYN. In bar 25, Xenakis changes the tempo to ♪ = 56 and then alternates both tempos every few bars. Xenakis called these interspersing sections "χάος" (chaos). The second section begins on bar 59, where the tempo changes to ♪ = 80. Here, Xenakis develops patterns that are based on the Fibonacci series. For example, the first percussionists starts a pattern with 21 thirty-second notes, then repeats the pattern with 13, then 8, and so on, until there are no more numbers left in the series, where he uses a roll ("ondulation" or glissando with the wrist) to turn around the series (first 1, then 2, then 3, then 5...). One of the only two appearances of the African bass drum is made near the end of this section. The third section begins on the third beat of bar 80, marked ♪ = 66. Here, Xenakis requires the percussionists to use a stick for high-pitched sounds and the hand to low-pitched sounds. He uses a "melodic-percussive rhythm" that was also used in Idmen B. The fourth section begins on the second beat of bar 104, marked ♪ = 92. The material in this section was developed using the same means as the automated material from the first section. The final section begins on bar 117. Even though Xenakis initially used ♪ = 70, he later changed his mind and used a slower tempo, ♪ = 56. According to Xenakis, the material used in this section is an exact copy of the music used in one of his other pieces for percussion, Rebonds A, composed that same year. The composer used different rhythms played over quintuplets and had two sections with polyrhythmic lines at tempo ♪ = 60 (bars 124-126 and, again, 130–132). Xenakis also used this method in Peaux. The piece ends at ♪ = 56, with a loud strike of the bass drum.

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