Chance

▶ Open in Aratu to hear the examples, change them and do the exercises

A loop that repeats exactly the same every time soon sounds mechanical. A drummer never plays two bars quite alike: a hi-hat note drops out, another appears. Chance gives a loop that life without you touching it: 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:

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tempo: 100
hh = cc cc c? cc
bd = b - b -

A percentage says how often:

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tempo: 100
hh = cc cc c?30% cc
sd = - s - s?80%

One or the other

Braces choose one of several options, separated by |, each time the loop comes round:

Try it▶ Hear it in Aratu

tempo: 100
bass = | {c2|g1} _ c2 _ |
hh = {cc|co} cc cc cc

The bass starts on C or on G; the hi-hat sometimes opens on the first beat.

The same chance again

The choices are drawn again every time round, but from a fixed seed: 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.

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seed 7
hh = c? c? c? c?

Changing one line does not change how the others improvise: each line draws on its own.

This lesson has no exercise to check, because chance has no right answer. Play with the examples as much as you like.