Cifra X is a sound and visual installation driven by a computer. The video displays a count up serie of integers starting from 1 and growing progressively at a speed of 3 per second.

Every number generates a beat: factorable numbers generate flat beats and prime numbers generate accented beats. The result is a 180 bpm rhythm with no bars, like a flux.

Since there is no rule that can predict the recurrence of primes in the natural numbers sequence, the rhythmic pattern you hear is absolutely non-repeating and unpredictable.

At the same time this pulsation has a very specific taste.
For example, there will never be two accented beats in a row because of even numbers (the only exception is the couple 2-3 that happens only once at the very beginning of the piece).

Also, there's one pattern that we find quite often in the sequence, that is the 1-0-1 of the p and p+2 couples (like 11-13, 17-19, 29-31 and so on).

Moreover, there will always be at every decade the 3 flat beats in a raw because of numbers ending with 4-5-6, that is never prime.

Many other less recognizable rules can be found in the beating but beside any mathematical cause, it still remains an intriguing and surprising musical rhythm to me.

Revised in 2022
When I conceived this piece in 2007, I wrote in the notes: "The duration of the piece depends on the computer power. The processing time in between the beats increases as the piece is played. The higher the number the longer the calculation the more absorbing CPU resources causes the piece tempo to gradually slow down and down. The piece ends when the calculating process absorbs all the CPU resources and the machine stucks."
At that time it would take just a few hours to start to slow down the tempo and a week maximum to get stuck for a common CPU. Today with my ordinary laptop it could go on for years and years at about the same speed without significative defaillances.