16. Chance

▶ Open in Aratu to hear and change the examples

A loop that repeats exactly the same soon sounds mechanical. Chance gives it life: the computer decides, a little at random, what to play each time round. It is the ad lib of a score.

Sometimes. A ? after a symbol plays it only some of the time, half of the time by default; a percentage sets how often:

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hh = cc cc c?30% cc
sd = - s - s?80%

One or the other. Braces choose one of several, separated by |, each time the loop comes round:

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bass = | {c2|g1} _ c2 _ |
hh   = {cc|co} cc cc cc

The same chance again. The choices are drawn again every time round, but from a fixed seed, so the same piece improvises the same way each time it is played from the start. seed 7 picks another improvisation; seed random makes every performance different. Changing one line does not change how the others improvise.