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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After 20 generations the expression "X" became this:
transpose((transpose(step(echo((transpose(transpose(echo(X,4,6) ,-5) ,-5) +transpose(transpose(transpose(transpose((step(transpose(X,-5) ,12) +transpose((X+shuffle(X) ) ,7) ) ,4) ,-7) ,-7) ,12) ) ,4,6) ,12) ,-5) |(((transpose(step(transpose(echo(transpose((shuffle(transpose(transpose(transpose(X,4) ,4) ,4) ) +transpose(arpeggio((X+X) ) ,4) ) ,4) ,4,6) ,-7) ,12) ,4) +(arpeggio(((transpose(transpose(echo((transpose(X,-7) +(transpose(transpose((X+transpose(X,12) ) ,-7) ,4) +transpose(arpeggio(X) ,7) ) ) ,4,6) ,4) ,4) |(((step((arpeggio(X) |(X+X) ) ,12) +transpose(transpose((transpose((X|step(X,12) ) ,-5) +(X+transpose(X,7) ) ) ,-5) ,7) ) +transpose((transpose(((X+transpose(transpose(X,-5) ,12) ) +transpose((X|X) ,7) ) ,4) |transpose(transpose(echo(transpose(transpose(X,-5) ,-7) ,4,6) ,4) ,-5) ) ,7) ) +transpose(transpose(transpose(((step(X,12) +(transpose(echo(X,4,6) ,4) +transpose(X,4) ) ) +(X+(X+transpose(X,7) ) ) ) ,4) ,-5) ,7) ) ) +transpose(step(transpose(transpose(transpose(transpose(shuffle(X) ,4) ,-5) ,-5) ,4) ,12) ,12) ) ) +shuffle(transpose(transpose(echo(transpose(((transpose(transpose(X,-5) ,-5) |transpose(transpose(X,-7) ,4) ) +echo(((X+transpose(X,7) ) +transpose(shuffle((X|X) ) ,12) ) ,4,6) ) ,-7) ,4,6) ,-5) ,-7) ) ) ) +transpose((shuffle((step((((transpose((arpeggio(X) +((X+transpose((X+X) ,4) ) +transpose(step(X,12) ,7) ) ) ,-7) +(((shuffle(step(X,12) ) +transpose(arpeggio(X) ,4) ) +transpose((X+transpose(X,12) ) ,7) ) +transpose((((transpose(X,-5) +transpose(arpeggio((X+X) ) ,7) ) +transpose(step(echo(X,4,6) ,12) ,4) ) +transpose(echo(transpose(shuffle(X) ,-5) ,4,6) ,7) ) ,12) ) ) +transpose(transpose(transpose(shuffle(X) ,-7) ,-5) ,-5) ) |arpeggio(arpeggio(shuffle((X|(X+X) ) ) ) ) ) ,12) +(transpose(((((X|((X+transpose(X,4) ) +transpose(X,7) ) ) +transpose(transpose(step(X,12) ,4) ,4) ) +transpose(transpose(echo((X+(X+transpose(X,12) ) ) ,4,6) ,-7) ,7) ) +transpose(((echo(X,4,6) +transpose(X,12) ) |transpose(step(X,12) ,4) ) ,-7) ) ,4) +((transpose(X,4) |arpeggio(step(transpose(X,-7) ,12) ) ) |transpose(step(transpose(shuffle(transpose(X,4) ) ,4) ,12) ,-5) ) ) ) ) +((transpose(transpose(((((((transpose(X,-5) +transpose((X+X) ,4) ) +transpose((X+X) ,7) ) +step(X,12) ) +transpose(step(transpose((X|X) ,4) ,12) ,4) ) +transpose(arpeggio(X) ,7) ) +transpose((X|(transpose(X,4) |shuffle(X) ) ) ,4) ) ,-5) ,-5) |transpose(((transpose(shuffle(((X+transpose(X,12) ) +(X+transpose(X,12) ) ) ) ,-5) +transpose((transpose((((X+transpose(step(X,12) ,12) ) +transpose(((X+X) +transpose(transpose(X,-7) ,12) ) ,4) ) +transpose(transpose(transpose(X,-7) ,-5) ,7) ) ,-7) |(transpose((X|X) ,-5) +((X+transpose(X,4) ) +transpose(X,7) ) ) ) ,4) ) +transpose(transpose((((echo(X,4,6) |(X+transpose(X,12) ) ) +transpose(step(echo(X,4,6) ,12) ,4) ) +transpose(arpeggio((X+X) ) ,7) ) ,-5) ,7) ) ,4) ) +transpose(((transpose(arpeggio((transpose(shuffle(X) ,-7) |echo(X,4,6) ) ) ,4) +transpose(step(((transpose(X,-5) |transpose(transpose(X,-5) ,4) ) +transpose(transpose(transpose(X,-7) ,4) ,7) ) ,12) ,12) ) |transpose((transpose(shuffle(step(X,12) ) ,-5) |((((X+transpose(X,12) ) +transpose(step(X,12) ,12) ) +transpose(X,-5) ) +X) ) ,-5) ) ,-7) ) ) ,7) ) |transpose((transpose((transpose(((X+transpose(transpose(X,-5) ,4) ) +transpose(((echo((X|X) ,4,6) +transpose(step(arpeggio(X) ,12) ,12) ) |transpose((X|X) ,-7) ) ,7) ) ,-7) |((X+echo(X,4,6) ) +(transpose(X,4) |(X+transpose(transpose(X,-5) ,12) ) ) ) ) ,4) |(echo(echo((((((echo(X,4,6) +(X+X) ) +transpose(transpose(X,4) ,4) ) +transpose(step(X,12) ,7) ) |((X|X) +(X|X) ) ) +transpose(arpeggio(transpose(X,-7) ) ,12) ) ,4,6) ,4,6) +transpose(arpeggio(echo(step((transpose((X|X) ,-7) +transpose(X,12) ) ,12) ,4,6) ) ,12) ) ) ,4) ) ) ,4)
random seed used was 164175387 EXPR = arpeggio((transpose(transpose((transpose(transpose(transpose((transpose(((((X+transpose(X,4) ) +transpose(X,7) ) +transpose(X,12) ) +((echo(X,4,6) +transpose(X,4) ) +transpose(shuffle((X+X) ) ,7) ) ) ,4) +transpose(((transpose(X,-7) +transpose((X+X) ,4) ) +transpose(X,7) ) ,-7) ) ,-7) ,4) ,-7) +(arpeggio(transpose(((shuffle(transpose((((shuffle(transpose(X,-7) ) +transpose(echo(transpose((X|X) ,4) ,4,6) ,4) ) +transpose(transpose(X,-5) ,7) ) +step(transpose(X,4) ,12) ) ,-5) ) +(transpose(((X+transpose(X,4) ) +transpose(transpose(X,4) ,7) ) ,4) +transpose(shuffle((transpose(((X+transpose(X,12) ) |X) ,4) +(transpose(X,4) +transpose(transpose(X,-7) ,7) ) ) ) ,12) ) ) +transpose(((arpeggio((X+transpose(X,7) ) ) +transpose(transpose(arpeggio((transpose((X+transpose(X,12) ) ,4) |echo(echo(X,4,6) ,4,6) ) ) ,4) ,7) ) +transpose(((((echo(X,4,6) |shuffle(X) ) +transpose(transpose(X,-5) ,7) ) +transpose(transpose(X,-7) ,7) ) |(transpose(step(X,12) ,-7) |arpeggio(transpose((X+transpose(X,12) ) ,-5) ) ) ) ,12) ) ,12) ) ,-5) ) +(transpose((transpose(((((X|transpose(X,-7) ) |(((X+transpose(X,4) ) +transpose((X+X) ,7) ) +X) ) +transpose(transpose(transpose(X,-5) ,4) ,12) ) |((echo((transpose((((X+X) +transpose(shuffle(X) ,4) ) +transpose((X|X) ,7) ) ,-5) +transpose((X+transpose(arpeggio(X) ,7) ) ,12) ) ,4,6) +transpose(transpose(((X|X) +transpose(shuffle(X) ,12) ) ,-5) ,4) ) +transpose(arpeggio((X+X) ) ,7) ) ) ,4) +transpose(transpose(arpeggio(transpose((transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-7) +step(X,12) ) ,4) ) ,4) ,12) ) ,-7) +transpose(arpeggio((((transpose(X,4) +shuffle(transpose(X,4) ) ) +transpose(transpose(transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-7) ,4) ,12) ) |(transpose(step(arpeggio((X+arpeggio((X|X) ) ) ) ,12) ,4) +transpose(transpose(step((shuffle(X) |(X|(X|X) ) ) ,12) ,4) ,-5) ) ) ) ,12) ) ) ) ,4) ,-5) +((((((arpeggio(transpose(transpose((((X|arpeggio(X) ) +transpose(X,4) ) +transpose(transpose((X+X) ,-5) ,7) ) ,-5) ,-5) ) +transpose(transpose((((transpose(shuffle(X) ,-7) +transpose(transpose(((X+transpose(X,12) ) +transpose(echo(X,4,6) ,7) ) ,-5) ,4) ) +transpose(((X+X) |((X+transpose(X,4) ) +transpose(X,7) ) ) ,7) ) +transpose((transpose((X+X) ,-7) +transpose(step(X,12) ,12) ) ,7) ) ,-5) ,7) ) +(echo(transpose(transpose((X+transpose(echo(transpose(echo(X,4,6) ,4) ,4,6) ,7) ) ,-7) ,4) ,4,6) +transpose(shuffle(transpose(transpose(transpose(transpose((((X+transpose(X,7) ) +transpose(X,7) ) +transpose(transpose((X+transpose(X,7) ) ,4) ,7) ) ,4) ,-5) ,4) ,-7) ) ,7) ) ) +transpose(shuffle((((transpose(step(X,12) ,4) +transpose(echo(X,4,6) ,12) ) +transpose((((transpose(X,-7) +((X|X) +X) ) +transpose(arpeggio(X) ,4) ) +transpose((transpose(echo(X,4,6) ,-5) +transpose((X+(X|X) ) ,12) ) ,7) ) ,12) ) |transpose((X+transpose(X,4) ) ,-7) ) ) ,7) ) |((((transpose(step(transpose((transpose(transpose(X,4) ,-7) |((arpeggio(X) +transpose(arpeggio(X) ,7) ) |transpose(X,4) ) ) ,-5) ,12) ,-7) +transpose(echo(((transpose(transpose(X,-7) ,-5) +transpose((transpose(X,-5) +arpeggio(X) ) ,12) ) |echo(echo(((X+transpose(X,12) ) +transpose(shuffle(X) ,12) ) ,4,6) ,4,6) ) ,4,6) ,4) ) |((((X+transpose(X,12) ) |step(X,12) ) +transpose((transpose((shuffle(shuffle(X) ) +transpose(shuffle((X+transpose(X,12) ) ) ,7) ) ,-5) +(((X|X) |echo(step(X,12) ,4,6) ) +transpose(arpeggio(transpose((X+X) ,-5) ) ,7) ) ) ,12) ) |step(echo((arpeggio((transpose(X,4) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,12) ) ) +(transpose(transpose(X,-5) ,-5) +transpose((X+(X+transpose(X,12) ) ) ,7) ) ) ,4,6) ,12) ) ) +transpose((arpeggio(transpose(transpose(echo(transpose((X+transpose(X,12) ) ,-5) ,4,6) ,-5) ,-7) ) |(transpose((transpose((X+transpose((X+transpose(X,7) ) ,12) ) ,-7) +transpose(echo(step(step(transpose(X,-5) ,12) ,12) ,4,6) ,12) ) ,4) +transpose((((transpose(X,4) +X) +transpose((((X+transpose(X,4) ) +transpose(X,7) ) +((X+transpose(X,4) ) +transpose(X,7) ) ) ,4) ) +transpose(transpose(shuffle(X) ,4) ,7) ) ,4) ) ) ,12) ) |transpose((arpeggio((X+arpeggio(X) ) ) +(((transpose(transpose(X,-5) ,-7) |step(((X+transpose((X|X) ,4) ) +transpose(X,7) ) ,12) ) +transpose((transpose(X,-5) +transpose(transpose(step(X,12) ,-5) ,12) ) ,7) ) +transpose(X,-7) ) ) ,4) ) ) +transpose((((((shuffle(transpose(transpose(X,-7) ,4) ) +transpose(transpose((transpose(X,4) +transpose(transpose(X,-7) ,7) ) ,4) ,4) ) +transpose(transpose(transpose(X,-7) ,-5) ,7) ) |(((((X+transpose((X|X) ,7) ) +transpose(X,4) ) +transpose((((X|X) +transpose(X,12) ) +(transpose(X,-5) +transpose(transpose(X,-7) ,12) ) ) ,7) ) +transpose(echo(((shuffle(step(X,12) ) +echo(X,4,6) ) +transpose(transpose(echo(X,4,6) ,-7) ,7) ) ,4,6) ,7) ) +((transpose((X+transpose(X,12) ) ,-5) +transpose(echo((X+transpose(X,12) ) ,4,6) ,4) ) +transpose(echo(transpose(X,-5) ,4,6) ,7) ) ) ) +transpose((((((transpose(X,-7) +transpose((X+transpose(X,7) ) ,12) ) +((X|X) +(X+transpose(X,12) ) ) ) +(transpose(X,-7) +transpose(echo(X,4,6) ,12) ) ) +transpose(((((X+X) |transpose(X,-5) ) +transpose((step(X,12) +transpose(transpose(X,-7) ,12) ) ,4) ) +transpose(((arpeggio(X) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,4) ) +transpose((X+transpose(X,7) ) ,7) ) ,7) ) ,4) ) +transpose(shuffle(((X+transpose((X+(X+transpose(X,12) ) ) ,4) ) +transpose((X+X) ,7) ) ) ,7) ) ,-5) ) +transpose(arpeggio(transpose((transpose(transpose(transpose(X,-5) ,4) ,-7) +transpose(transpose(X,-5) ,12) ) ,-5) ) ,4) ) ,-7) ) |(arpeggio(step(((((echo(X,4,6) +transpose((X+transpose(X,7) ) ,4) ) +transpose(transpose((X+X) ,-7) ,7) ) +echo(arpeggio(X) ,4,6) ) +transpose(shuffle(transpose(shuffle(transpose(X,4) ) ,-7) ) ,12) ) ,12) ) +transpose(((transpose(((transpose(X,-7) |transpose(echo((X+transpose(transpose(X,-5) ,12) ) ,4,6) ,-5) ) +arpeggio(((X+transpose(X,4) ) +transpose(X,7) ) ) ) ,-5) +transpose(((step(transpose(transpose((X+X) ,-5) ,-5) ,12) |transpose((step((arpeggio(((X+transpose(X,4) ) +transpose(X,7) ) ) +(X+X) ) ,12) |shuffle((transpose(transpose(X,4) ,-5) +X) ) ) ,-7) ) +((transpose(echo(transpose(X,-5) ,4,6) ,-5) +transpose(echo((((transpose(((X+transpose(X,12) ) +transpose(X,12) ) ,-7) +transpose(((X+transpose(X,7) ) |transpose(X,-5) ) ,12) ) +transpose((arpeggio((X+transpose(X,12) ) ) +transpose((((X+transpose(X,4) ) +transpose(X,7) ) |echo(X,4,6) ) ,7) ) ,12) ) +transpose(step((X+transpose(X,12) ) ,12) ,7) ) ,4,6) ,4) ) +transpose(transpose(transpose((transpose(shuffle(transpose(X,-7) ) ,4) |(shuffle((X+transpose(X,12) ) ) +transpose(echo((X|X) ,4,6) ,12) ) ) ,4) ,4) ,7) ) ) ,4) ) +transpose(transpose(step((transpose(((arpeggio(X) |(((X+X) +transpose(X,4) ) +transpose(X,7) ) ) +((X+transpose(transpose(X,4) ,7) ) +transpose(echo(X,4,6) ,-5) ) ) ,-5) |(transpose(transpose(transpose(((X+transpose(X,7) ) +X) ,4) ,-5) ,4) +transpose(transpose((((X|((X+X) +transpose(X,7) ) ) +transpose(step(transpose(X,-5) ,12) ,4) ) +transpose((((transpose(X,4) +transpose(X,4) ) +transpose((X+X) ,7) ) +transpose((X|X) ,-7) ) ,7) ) ,-7) ,7) ) ) ,12) ,-7) ,7) ) ,-5) ) ) ) )
random seed used was 0

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