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

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