Home : Tune Toys : Expresso 
  Expresso takes a simple musical expression (literally "X") and mutates it. In each generation, transformations are applied to components of the expression. This is a fractal technique known as an L-system. The more generations there are, the larger and more complex the expression gets (and the longer it can take to compute). The output varies wildly, from boring to fascinating. Press "Mutate" a few times till you get something that looks interesting, then click on the image to play it. See Composer's Quarry for examples of output.

Transformations:
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Phrase for X:
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After 20 generations the expression "X" became this:
transpose((echo(echo(step((transpose(transpose(((transpose((arpeggio(X) |((X|X) |X) ) ,-5) +transpose(step(transpose((X+transpose(X,7) ) ,-7) ,12) ,4) ) +transpose(((transpose(X,-7) +transpose(X,12) ) +transpose(((X+X) |(X+X) ) ,12) ) ,7) ) ,4) ,4) +transpose((echo((transpose(step(transpose((transpose(X,4) +transpose(echo(((X+transpose(X,4) ) +transpose(X,7) ) ,4,6) ,12) ) ,4) ,12) ,-7) +transpose(transpose((X+X) ,4) ,4) ) ,4,6) +((transpose(transpose((X+X) ,-7) ,-5) |transpose((transpose(X,4) |X) ,-5) ) |(transpose(transpose(X,-5) ,4) +transpose((transpose(X,4) +transpose(X,7) ) ,-7) ) ) ) ,4) ) ,12) ,4,6) ,4,6) +transpose((transpose((transpose(shuffle(((transpose(echo((transpose(((arpeggio(X) +transpose(X,12) ) |((((X+X) +transpose(shuffle(X) ,7) ) +transpose(transpose(X,4) ,4) ) +transpose((X+X) ,7) ) ) ,-7) +transpose((X+transpose(arpeggio(X) ,12) ) ,7) ) ,4,6) ,4) +transpose(transpose(transpose(transpose((((transpose(X,-5) |echo(X,4,6) ) +transpose(step(X,12) ,12) ) +transpose(transpose(X,4) ,7) ) ,-5) ,4) ,4) ,4) ) +transpose((transpose(shuffle(transpose(echo((transpose(X,-7) +transpose(shuffle(X) ,7) ) ,4,6) ,4) ) ,4) |(transpose(transpose(((transpose(step((X+X) ,12) ,4) +transpose(((X|X) +arpeggio(echo(X,4,6) ) ) ,7) ) +((transpose(echo(X,4,6) ,-5) +transpose(shuffle((X+X) ) ,4) ) +transpose((transpose(X,4) +transpose((transpose(X,-5) +transpose((X+transpose(X,7) ) ,7) ) ,7) ) ,7) ) ) ,-7) ,4) +arpeggio(echo(((transpose(transpose(X,-5) ,-5) +transpose(transpose(X,-7) ,4) ) +transpose(step(X,12) ,7) ) ,4,6) ) ) ) ,7) ) ) ,-5) +(((echo(transpose(transpose(transpose((((X|X) |(X+transpose(X,7) ) ) +transpose((X+transpose(X,12) ) ,12) ) ,4) ,4) ,4) ,4,6) +transpose(((arpeggio(((X|X) |((X+X) +(X+transpose(X,7) ) ) ) ) +transpose(((transpose((shuffle(X) +X) ,4) +transpose(transpose((transpose((X+X) ,4) |echo(X,4,6) ) ,4) ,7) ) +(echo(X,4,6) |(((X+transpose(X,-7) ) +transpose(((X+X) +((transpose(arpeggio(X) ,4) +transpose(transpose(X,-7) ,4) ) +transpose((((X+transpose(X,12) ) +transpose(transpose(X,-7) ,4) ) +transpose(transpose(X,-5) ,7) ) ,7) ) ) ,12) ) +(transpose(X,4) |(X+transpose(X,-5) ) ) ) ) ) ,12) ) +transpose((((((transpose(transpose((X+X) ,4) ,4) +transpose((transpose(transpose((X+transpose(X,7) ) ,4) ,-5) +(((X+transpose(X,-5) ) |transpose(X,-7) ) |((X+X) +transpose((((X+transpose(X,4) ) +transpose(X,7) ) +(X+arpeggio(X) ) ) ,12) ) ) ) ,4) ) +transpose(shuffle(arpeggio(transpose((X+X) ,-5) ) ) ,7) ) +transpose(transpose(transpose((step(transpose((transpose(X,-5) +transpose(transpose(X,-5) ,12) ) ,-5) ,12) +transpose(transpose(step(X,12) ,4) ,7) ) ,-5) ,4) ,4) ) +transpose(transpose((transpose(arpeggio(X) ,4) +transpose(transpose((transpose(transpose(X,4) ,-5) +transpose(X,4) ) ,-5) ,12) ) ,-5) ,7) ) |((transpose(X,-7) |((echo(X,4,6) +transpose(((step(X,12) +transpose(X,4) ) +transpose(transpose(X,4) ,7) ) ,7) ) +transpose(transpose((X|X) ,4) ,12) ) ) +transpose(transpose(transpose(arpeggio(transpose(transpose(step(X,12) ,4) ,4) ) ,-5) ,4) ,7) ) ) ,7) ) ,4) ) +transpose(arpeggio(((((transpose(transpose(transpose(transpose(transpose(transpose(X,4) ,4) ,4) ,-7) ,4) ,-5) +transpose(((echo(transpose(X,-5) ,4,6) +transpose((((transpose(transpose((X+transpose(X,7) ) ,4) ,-7) |(X|transpose((X+transpose(X,12) ) ,-7) ) ) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-7) ) |arpeggio(X) ) ,4) ) +transpose(step(step(transpose(transpose(X,-7) ,4) ,12) ,12) ,7) ) ,4) ) +transpose(transpose(X,-7) ,7) ) |transpose((arpeggio((((X+X) +transpose(arpeggio(X) ,7) ) +transpose(((transpose(step(X,12) ,4) +transpose(((((X+transpose(X,4) ) +transpose(X,7) ) +transpose((X+X) ,4) ) +transpose(X,7) ) ,4) ) +transpose(step(X,12) ,7) ) ,12) ) ) +transpose(arpeggio(transpose((transpose(X,-5) |X) ,-7) ) ,12) ) ,4) ) +transpose((transpose(shuffle((((X+X) |transpose(X,-5) ) +transpose(step(X,12) ,7) ) ) ,4) +transpose(transpose(transpose((transpose((X|X) ,4) +((X+transpose(X,7) ) +transpose(transpose((X|X) ,4) ,7) ) ) ,-7) ,4) ,4) ) ,12) ) ) ,7) ) +transpose(((((transpose(step(step(transpose(X,4) ,12) ,12) ,-7) +transpose(transpose(arpeggio(((X+transpose(X,12) ) +X) ) ,4) ,7) ) +transpose(transpose(((echo(((X+transpose(X,12) ) +transpose(echo(X,4,6) ,7) ) ,4,6) +(((X+X) +X) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,12) ) ) |transpose((X+(X+transpose(X,7) ) ) ,-5) ) ,4) ,7) ) +shuffle(transpose(arpeggio(transpose((shuffle(transpose(X,-7) ) +transpose((transpose(X,-5) |(X+X) ) ,12) ) ,4) ) ,-5) ) ) |transpose(transpose(((transpose((X+transpose(X,12) ) ,-5) +transpose((X+(transpose(X,4) +transpose(transpose(X,-5) ,7) ) ) ,12) ) +((shuffle(X) +X) +transpose(((((X+transpose(X,7) ) +(X|X) ) +transpose(arpeggio(transpose((X|X) ,4) ) ,4) ) +transpose((arpeggio(X) +((X+transpose(X,7) ) |shuffle(X) ) ) ,7) ) ,7) ) ) ,4) ,-7) ) ,7) ) ) ,4) |(((((arpeggio(transpose(X,-7) ) +transpose((shuffle((transpose((transpose(X,4) +((X+transpose(X,4) ) +transpose(X,7) ) ) ,-7) +transpose(step((((X|X) +shuffle(step(X,12) ) ) |((X+transpose(X,12) ) +transpose(X,12) ) ) ,12) ,7) ) ) +transpose(((transpose((transpose((X|X) ,-5) +transpose(transpose(echo(X,4,6) ,4) ,7) ) ,4) +transpose((X+X) ,4) ) +transpose(arpeggio(transpose((transpose(X,4) +transpose(step(X,12) ,12) ) ,-7) ) ,7) ) ,7) ) ,7) ) |(((step(transpose(X,-5) ,12) +(transpose(X,-5) +shuffle(X) ) ) +arpeggio(((arpeggio(X) +transpose(transpose(X,-7) ,12) ) |((X|X) +transpose(arpeggio(X) ,12) ) ) ) ) |arpeggio(transpose(((transpose(transpose(echo(transpose(X,4) ,4,6) ,-5) ,-7) +transpose(((transpose((X+step(X,12) ) ,-5) +transpose((X|X) ,4) ) +transpose((X+transpose(X,7) ) ,7) ) ,4) ) +transpose((((transpose((X+transpose(X,7) ) ,4) +transpose(echo(X,4,6) ,-5) ) +transpose(X,4) ) +transpose(echo(transpose(X,-5) ,4,6) ,7) ) ,7) ) ,4) ) ) ) |arpeggio((transpose((transpose((arpeggio((X+X) ) |X) ,-7) +transpose((((((X+X) |(X+transpose(X,7) ) ) +((X+transpose(X,12) ) +transpose(X,7) ) ) +transpose(transpose(transpose((X|X) ,-5) ,-7) ,4) ) +transpose(shuffle((transpose(X,4) +transpose(transpose(X,-7) ,7) ) ) ,7) ) ,-5) ) ,4) +step(transpose(((shuffle((X+transpose(X,7) ) ) +((arpeggio(X) +transpose((X+X) ,7) ) |((X+transpose(X,4) ) +transpose(X,7) ) ) ) |(step(echo(((X+transpose(X,4) ) +transpose(X,7) ) ,4,6) ,12) +shuffle((X+X) ) ) ) ,-7) ,12) ) ) ) +transpose((transpose(transpose(transpose(((transpose(echo((X+X) ,4,6) ,-5) +(arpeggio(X) |transpose(arpeggio(X) ,-7) ) ) +step((arpeggio((echo(X,4,6) +transpose(X,7) ) ) +transpose((X+transpose(step(transpose(X,4) ,12) ,7) ) ,7) ) ,12) ) ,-7) ,-5) ,-5) |arpeggio(((((X+transpose(transpose(X,-7) ,4) ) +transpose((transpose(X,4) +(X|X) ) ,7) ) +(((echo(X,4,6) +transpose(transpose(X,-5) ,7) ) |transpose((transpose(X,-5) |step(X,12) ) ,4) ) +(((X+transpose(step(X,12) ,-7) ) +transpose(transpose(transpose(X,-5) ,4) ,4) ) +transpose((arpeggio(X) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,12) ) ,7) ) ) ) +transpose((transpose(((((echo(X,4,6) +transpose((((X|X) |X) +transpose(((X|X) +transpose(X,-7) ) ,7) ) ,7) ) +transpose(transpose(((X+transpose(X,12) ) +transpose((X+X) ,7) ) ,-5) ,-5) ) +transpose(transpose(transpose((X+transpose((X|X) ,7) ) ,4) ,-5) ,4) ) +transpose(shuffle(transpose(echo(((shuffle(X) +transpose(transpose(X,-5) ,4) ) +transpose(X,7) ) ,4,6) ,-5) ) ,7) ) ,4) +transpose(arpeggio((transpose(echo((X+transpose(X,7) ) ,4,6) ,4) +transpose(transpose(echo(((X+transpose(X,12) ) +step(X,12) ) ,4,6) ,-5) ,12) ) ) ,-7) ) ,12) ) ) ) ,4) ) +transpose(transpose((((echo(step(echo((transpose(((X+transpose((X|X) ,7) ) +arpeggio(X) ) ,-7) +transpose(((((X+transpose(X,-5) ) +transpose(((X|X) +transpose(X,-7) ) ,4) ) +transpose(echo(X,4,6) ,7) ) |transpose(step(transpose(X,-7) ,12) ,-5) ) ,7) ) ,4,6) ,12) ,4,6) +transpose(echo((transpose(transpose(arpeggio(((X+transpose(X,12) ) +X) ) ,-7) ,4) +step(transpose(step((transpose((X+transpose(X,7) ) ,-7) +arpeggio(X) ) ,12) ,-7) ,12) ) ,4,6) ,7) ) |(echo((transpose(arpeggio(shuffle(X) ) ,4) +(((shuffle((X|X) ) +((X+transpose(X,12) ) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,7) ) ) |transpose(transpose(transpose((X+X) ,-7) ,-5) ,-7) ) +transpose(shuffle(transpose((((X+transpose(X,4) ) +transpose(step(X,12) ,7) ) |transpose(transpose(X,4) ,-5) ) ,-7) ) ,7) ) ) ,4,6) +transpose(((transpose((transpose(((X+X) +transpose(X,7) ) ,4) +transpose(arpeggio((arpeggio(X) +transpose((X|X) ,12) ) ) ,7) ) ,-5) |(((((X+transpose((X+X) ,12) ) +transpose(X,12) ) +transpose(transpose(transpose(X,-7) ,-5) ,7) ) +transpose(echo(X,4,6) ,7) ) +transpose(transpose(X,-7) ,12) ) ) |transpose((X+(((X+transpose((X+transpose(X,12) ) ,4) ) +transpose((X+transpose(X,12) ) ,7) ) +(X+X) ) ) ,4) ) ,7) ) ) +(((transpose(transpose(transpose(transpose(X,-5) ,-5) ,-7) ,-7) +transpose(((transpose(transpose(transpose(X,4) ,4) ,4) +(arpeggio(X) +transpose(X,4) ) ) +transpose(step(shuffle((X|(X+transpose(X,7) ) ) ) ,12) ,12) ) ,7) ) +transpose(((transpose(echo((shuffle(X) |X) ,4,6) ,-7) +((transpose(X,-7) |(X|(X|X) ) ) |transpose((transpose((X+transpose(X,7) ) ,-5) |transpose((X+transpose(X,12) ) ,-5) ) ,-7) ) ) +((((step(transpose(X,-5) ,12) +transpose(arpeggio((((X+transpose(X,12) ) +transpose((X+X) ,12) ) +transpose((X+transpose(X,7) ) ,7) ) ) ,4) ) +transpose(transpose(transpose(transpose((X+X) ,-5) ,4) ,-7) ,7) ) |((shuffle((X+transpose(X,12) ) ) +transpose(transpose(step((X+X) ,12) ,4) ,12) ) +transpose(transpose(echo(transpose(X,-7) ,4,6) ,-5) ,12) ) ) |echo(step(arpeggio(X) ,12) ,4,6) ) ) ,4) ) +transpose(transpose(((arpeggio(step((((X+X) +transpose(X,7) ) |transpose(X,-5) ) ,12) ) +((transpose(X,-7) +transpose(transpose(X,-7) ,12) ) +transpose(transpose((step(transpose(X,-5) ,12) +shuffle(X) ) ,-5) ,12) ) ) +step(((X+X) +transpose(transpose(shuffle(X) ,-7) ,12) ) ,12) ) ,-5) ,7) ) ) ,-5) ,7) ) ) ,12) ) ,-7)
random seed used was 216914821

The algorithm for Expresso is written in KeyKit, and here's the source code.