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(((transpose(((step(transpose((((X+X) +transpose(transpose(X,4) ,7) ) |((X+transpose(X,7) ) +transpose(echo(X,4,6) ,-5) ) ) ,4) ,12) +transpose(((step((step(arpeggio(X) ,12) +(arpeggio(transpose(X,-5) ) +((X|X) |(X|X) ) ) ) ,12) +transpose(transpose((((((arpeggio(X) |echo(X,4,6) ) +transpose(step(X,12) ,12) ) +transpose((X+X) ,4) ) +transpose(((shuffle(X) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,12) ) +(X+((X+transpose(X,4) ) +transpose(X,7) ) ) ) ,7) ) +transpose(((echo(X,4,6) |step(X,12) ) +transpose(((X|X) +transpose((X+transpose(X,12) ) ,12) ) ,12) ) ,7) ) ,-5) ,4) ) +transpose(transpose((transpose(step(X,12) ,-7) +transpose(echo((X+transpose(X,7) ) ,4,6) ,4) ) ,-7) ,7) ) ,4) ) +transpose(((((shuffle(step(transpose(X,-7) ,12) ) +arpeggio(((X+transpose(step(X,12) ,4) ) +transpose(echo(X,4,6) ,7) ) ) ) +(transpose((transpose(X,4) +transpose(arpeggio(X) ,7) ) ,-5) |transpose(X,-5) ) ) +step(transpose(transpose(arpeggio(X) ,-5) ,4) ,12) ) +transpose(shuffle((((transpose(step(X,12) ,4) |transpose(X,-7) ) +transpose(((X+X) +transpose((X|X) ,4) ) ,4) ) +transpose((transpose(transpose(X,-5) ,-7) +shuffle(X) ) ,7) ) ) ,12) ) ,7) ) ,4) +transpose(transpose(transpose((((transpose(((((X|X) +transpose(echo(X,4,6) ,7) ) +transpose(shuffle(((X+transpose(X,4) ) +transpose(X,7) ) ) ,7) ) |transpose(echo(X,4,6) ,-5) ) ,4) +transpose(transpose(((X+transpose(X,12) ) |arpeggio((X+X) ) ) ,4) ,-5) ) |arpeggio(arpeggio(step((transpose(X,4) +transpose((X+transpose(X,7) ) ,7) ) ,12) ) ) ) +transpose(transpose(((((((transpose(arpeggio((transpose(X,4) +transpose((X|X) ,7) ) ) ,-7) |step(transpose(X,-7) ,12) ) +transpose(shuffle(echo(shuffle(X) ,4,6) ) ,4) ) +transpose((transpose(echo((X+X) ,4,6) ,4) +(X+arpeggio((X+X) ) ) ) ,7) ) +(((transpose(transpose(X,-7) ,4) +transpose((transpose(X,4) +transpose(transpose(X,-5) ,12) ) ,7) ) +transpose((((X+transpose((X+transpose(X,12) ) ,4) ) +transpose(echo(X,4,6) ,7) ) |(X+transpose(X,7) ) ) ,4) ) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,7) ) ) +transpose(transpose((shuffle(transpose(X,4) ) +transpose(step(X,12) ,7) ) ,4) ,4) ) +transpose(echo(transpose(transpose(X,4) ,4) ,4,6) ,7) ) ,-5) ,7) ) ,-7) ,-7) ,4) ) +transpose((arpeggio(transpose(transpose(transpose((X+transpose((X+X) ,4) ) ,4) ,4) ,4) ) +step((step((transpose(transpose(X,4) ,-7) +transpose(shuffle((transpose(X,4) +transpose(X,12) ) ) ,12) ) ,12) |(echo(transpose((transpose(shuffle(arpeggio(X) ) ,-5) +transpose(((X|X) |X) ,-5) ) ,4) ,4,6) |step(transpose(arpeggio(X) ,-7) ,12) ) ) ,12) ) ,7) ) ,-5) +transpose(transpose((((step(echo((((((transpose((X+X) ,-7) +transpose((transpose(X,-5) +transpose((X|X) ,7) ) ,12) ) +arpeggio((X+transpose(X,7) ) ) ) +((transpose(X,-7) +transpose(transpose(transpose(transpose(X,-5) ,-5) ,-7) ,4) ) +transpose((transpose(X,4) +((X+transpose(X,4) ) +transpose(X,7) ) ) ,7) ) ) +transpose(transpose(transpose((step(X,12) +X) ,4) ,-7) ,12) ) +transpose(transpose(transpose(transpose(transpose((step(((X|X) +transpose(X,-5) ) ,12) +step((transpose(transpose(X,-5) ,-7) |(arpeggio(X) +((X+transpose(X,4) ) +transpose(X,7) ) ) ) ,12) ) ,-5) ,4) ,-7) ,4) ,7) ) ,4,6) ,12) +transpose(shuffle(step((transpose(transpose(transpose(transpose(transpose(step(X,12) ,-5) ,-5) ,-7) ,-5) ,4) |transpose(((transpose(transpose(echo(X,4,6) ,4) ,-5) +transpose(shuffle(X) ,-5) ) +((transpose((X+transpose(transpose(X,-7) ,7) ) ,-5) +transpose((((((X+transpose(X,4) ) +transpose(X,7) ) +transpose(X,7) ) +transpose(transpose((X+transpose(X,7) ) ,4) ,4) ) +transpose(((X+transpose(X,12) ) +transpose(shuffle(X) ,12) ) ,7) ) ,7) ) +transpose(echo(transpose(shuffle(X) ,4) ,4,6) ,12) ) ) ,4) ) ,12) ) ,4) ) +transpose((transpose(transpose((echo((transpose(transpose(transpose((X+transpose(X,12) ) ,-5) ,-7) ,-5) |transpose(((shuffle(transpose(shuffle(X) ,-7) ) +transpose(arpeggio(X) ,12) ) +(((transpose(X,-5) +transpose(X,-5) ) +transpose(X,-5) ) +transpose(transpose(X,4) ,4) ) ) ,4) ) ,4,6) +transpose((transpose((echo((X+X) ,4,6) +transpose((X+transpose(X,4) ) ,7) ) ,-7) +((X|X) +transpose(X,12) ) ) ,7) ) ,-7) ,-7) +transpose((transpose(transpose(transpose(arpeggio(echo((transpose(step(X,12) ,-5) |transpose((X|(X|X) ) ,-5) ) ,4,6) ) ,4) ,-5) ,4) +transpose(((((transpose(((transpose((X+transpose(X,12) ) ,4) +transpose(((((X+transpose(X,4) ) +transpose(X,7) ) +transpose(X,4) ) +transpose((X+transpose(X,12) ) ,7) ) ,12) ) +transpose(step(X,12) ,-5) ) ,-5) +transpose((shuffle((transpose((X+transpose(X,7) ) ,-5) +transpose(transpose(X,-7) ,12) ) ) +transpose(transpose((transpose(X,4) |transpose(X,4) ) ,-5) ,7) ) ,12) ) |(((echo(transpose(X,4) ,4,6) +transpose(transpose(transpose(echo(X,4,6) ,-5) ,4) ,4) ) +transpose(echo(transpose(X,-7) ,4,6) ,7) ) +arpeggio(arpeggio((X|X) ) ) ) ) +transpose((((X|X) +(((X|X) +transpose(transpose((shuffle(X) |((X+transpose(X,4) ) +transpose(X,7) ) ) ,4) ,7) ) +transpose(step((echo((X|X) ,4,6) +transpose((transpose(X,4) +(X+X) ) ,12) ) ,12) ,7) ) ) |((transpose(echo((X+transpose(X,12) ) ,4,6) ,-5) +transpose(step(((X|(transpose(X,4) |X) ) +transpose((transpose(X,-7) +transpose(X,12) ) ,-5) ) ,12) ,4) ) +transpose(transpose(((X+X) +((X+transpose(transpose(X,-5) ,4) ) +transpose((transpose(X,4) +transpose(X,-5) ) ,7) ) ) ,-5) ,7) ) ) ,4) ) +transpose(transpose(((((((X+transpose(X,4) ) +transpose(X,7) ) +transpose(shuffle(shuffle(transpose(X,-7) ) ) ,4) ) +transpose(transpose((X|X) ,4) ,7) ) +((X|X) +transpose((((((X+transpose(X,12) ) +transpose(X,7) ) +transpose(X,4) ) +transpose(shuffle(transpose(X,-7) ) ,7) ) +transpose(((transpose(X,-7) |transpose(X,-5) ) +transpose((X+transpose(X,7) ) ,7) ) ,12) ) ,7) ) ) +(((X+transpose(X,4) ) +transpose(arpeggio(X) ,7) ) +transpose(transpose(X,-5) ,12) ) ) ,-7) ,7) ) ,12) ) ,7) ) ,7) ) +transpose(arpeggio(transpose(((transpose(((((shuffle((transpose(transpose(X,-5) ,-5) +((X+X) +X) ) ) +transpose(transpose((X+X) ,-5) ,4) ) +transpose(transpose((X+transpose(transpose(X,4) ,12) ) ,4) ,7) ) +transpose((transpose(step(X,12) ,-7) +transpose((X+transpose(echo(X,4,6) ,12) ) ,12) ) ,4) ) +transpose(shuffle((arpeggio(((((X+transpose(X,4) ) +transpose(X,7) ) |transpose(X,4) ) +X) ) +echo(step(((arpeggio((X+transpose(X,12) ) ) +transpose((((X+transpose(X,12) ) +transpose((X+X) ,4) ) +transpose(X,7) ) ,4) ) +transpose((X+X) ,7) ) ,12) ,4,6) ) ) ,7) ) ,4) +(arpeggio(transpose(((((X+transpose((((X+transpose((X+transpose(X,7) ) ,4) ) +transpose((X+X) ,7) ) +transpose(X,-5) ) ,4) ) +transpose((arpeggio(X) |X) ,7) ) |transpose((transpose(X,-5) |((X+transpose(X,4) ) +transpose(X,7) ) ) ,-5) ) +echo(X,4,6) ) ,4) ) +transpose(transpose(transpose(((transpose(X,-5) |echo(X,4,6) ) |transpose(transpose(transpose(X,-7) ,-7) ,-5) ) ,4) ,4) ,-5) ) ) |transpose(((((step(X,12) +transpose(transpose(transpose(((step(arpeggio(X) ,12) +transpose(transpose((echo(X,4,6) +(X+transpose(transpose(X,-5) ,7) ) ) ,-5) ,4) ) +transpose(echo(((X+transpose((X+transpose((X|X) ,7) ) ,4) ) +transpose(echo(step(X,12) ,4,6) ,7) ) ,4,6) ,7) ) ,-5) ,-5) ,12) ) +transpose((transpose(transpose(transpose(X,4) ,-7) ,-5) +transpose((shuffle(arpeggio((X|X) ) ) +transpose((((X+transpose(X,7) ) +transpose(((X+transpose(X,12) ) +transpose(X,-7) ) ,7) ) +transpose(X,-7) ) ,12) ) ,12) ) ,4) ) +transpose(transpose(((transpose(transpose(step(((X+transpose(X,12) ) +transpose(echo((X|X) ,4,6) ,7) ) ,12) ,-7) ,4) +transpose(((((X|X) +transpose((X+transpose(X,12) ) ,7) ) +transpose((X|(X+transpose(X,12) ) ) ,7) ) +((echo((transpose(X,4) +transpose((X|X) ,7) ) ,4,6) +transpose((X+transpose(X,12) ) ,7) ) |transpose(X,-5) ) ) ,12) ) |((((((shuffle(X) +transpose(X,4) ) +transpose(step(X,12) ,7) ) +transpose(shuffle(step(X,12) ) ,4) ) +transpose(transpose((transpose(arpeggio(X) ,4) |((X+transpose(X,12) ) +transpose(X,7) ) ) ,-5) ,7) ) +transpose((arpeggio(arpeggio(X) ) +transpose(step(echo(X,4,6) ,12) ,7) ) ,12) ) |((((X+transpose((transpose(X,-5) +X) ,4) ) +transpose(transpose(X,-5) ,7) ) |((X+transpose(X,12) ) +transpose((transpose(X,-7) +X) ,7) ) ) |transpose(arpeggio(transpose(X,-5) ) ,-7) ) ) ) ,-5) ,7) ) +transpose(shuffle(transpose(transpose(transpose(step((arpeggio(X) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,7) ) ,12) ,4) ,-5) ,-7) ) ,12) ) ,-5) ) ,-5) ) ,7) ) ,-5) ,12) )
random seed used was 145863166

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