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 18 generations the expression "X" became this:
((((transpose((step(arpeggio((((shuffle(((echo(arpeggio(X) ,4,6) +transpose(transpose(X,-7) ,4) ) +transpose(transpose((X+transpose(X,7) ) ,-7) ,7) ) ) +arpeggio((transpose((X+transpose(X,12) ) ,-7) |(transpose(X,4) +transpose(X,7) ) ) ) ) +transpose(transpose(shuffle(echo((((X+transpose(X,12) ) +transpose((X+transpose(X,12) ) ,7) ) |(X+transpose((X+transpose(X,12) ) ,12) ) ) ,4,6) ) ,-5) ,4) ) +transpose(transpose(transpose((transpose(transpose(transpose(X,4) ,-7) ,-5) +transpose(transpose(echo(shuffle(X) ,4,6) ,4) ,7) ) ,-5) ,-7) ,7) ) ) ,12) |transpose(((transpose((X+transpose(X,7) ) ,-7) +transpose((transpose(X,-7) +(X+transpose(X,7) ) ) ,12) ) |((transpose(X,-7) |((transpose(transpose(transpose(X,-7) ,4) ,-5) +transpose(transpose(transpose(shuffle(X) ,4) ,4) ,7) ) |arpeggio((X+transpose(X,12) ) ) ) ) +transpose((transpose((arpeggio((transpose(X,-7) +transpose((X|X) ,7) ) ) +transpose(transpose((((X|X) +transpose(echo(X,4,6) ,4) ) +transpose(transpose(X,-5) ,7) ) ,-7) ,12) ) ,-7) |((transpose(arpeggio(X) ,-7) +transpose(transpose((X+transpose(echo(X,4,6) ,7) ) ,-5) ,4) ) +transpose(transpose(arpeggio(arpeggio(X) ) ,-5) ,7) ) ) ,12) ) ) ,4) ) ,-5) +transpose(transpose((echo(echo(((step(((((((echo(X,4,6) +transpose((X+transpose(X,7) ) ,4) ) +transpose(transpose(X,-7) ,7) ) |(X+transpose((X+transpose(X,12) ) ,7) ) ) |((arpeggio(X) +transpose(transpose(X,4) ,4) ) +transpose(transpose(X,-5) ,7) ) ) |transpose(X,-5) ) +shuffle(transpose(echo(transpose(X,-7) ,4,6) ,-5) ) ) ,12) +transpose((shuffle(((transpose(transpose(arpeggio(X) ,-5) ,-5) |echo(arpeggio(X) ,4,6) ) +transpose(transpose(echo(transpose(X,-5) ,4,6) ,4) ,12) ) ) |(step(echo(X,4,6) ,12) +transpose(arpeggio(transpose(((arpeggio(transpose(X,-5) ) +transpose(echo((X|X) ,4,6) ,12) ) |((transpose((X+transpose(X,12) ) ,-5) +transpose((X|(X+transpose(X,12) ) ) ,4) ) +transpose(transpose((X+transpose(X,12) ) ,-7) ,7) ) ) ,4) ) ,12) ) ) ,4) ) +transpose((((transpose(transpose((transpose(X,4) |transpose((((X+transpose(X,4) ) +transpose(X,7) ) +transpose(step(X,12) ,12) ) ,4) ) ,4) ,4) |((arpeggio(echo(echo(X,4,6) ,4,6) ) +transpose(transpose(transpose(transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-5) ,-7) ,-5) ,7) ) +transpose(echo(X,4,6) ,12) ) ) +transpose(step(transpose((transpose((transpose((X+transpose(X,12) ) ,-5) |step((X+transpose(X,7) ) ,12) ) ,-7) +transpose(transpose(arpeggio((X+transpose(X,12) ) ) ,4) ,12) ) ,4) ,12) ,12) ) +transpose((transpose(((step(X,12) +transpose(((X+transpose(X,4) ) +transpose(echo(arpeggio(X) ,4,6) ,7) ) ,7) ) +transpose(echo((X+X) ,4,6) ,12) ) ,4) |((echo(transpose(X,4) ,4,6) +transpose(transpose(arpeggio(transpose(((X+transpose(shuffle(X) ,4) ) +transpose(transpose(X,-5) ,7) ) ,4) ) ,-7) ,4) ) +transpose((transpose(transpose((X+transpose(X,7) ) ,-7) ,-7) +transpose((transpose((transpose(X,-5) +X) ,4) |transpose(((X+transpose(X,12) ) +((X|X) +transpose(step(X,12) ,7) ) ) ,-5) ) ,7) ) ,7) ) ) ,12) ) ,7) ) ,4,6) ,4,6) |((transpose((shuffle((transpose((transpose(echo(X,4,6) ,-7) +transpose(X,7) ) ,4) +((transpose(X,4) |transpose(X,-7) ) +((X+transpose(X,4) ) +transpose(shuffle(X) ,7) ) ) ) ) +transpose(arpeggio(transpose(transpose((transpose((X+transpose(X,7) ) ,-7) |echo(shuffle(step(X,12) ) ,4,6) ) ,-5) ,-5) ) ,7) ) ,4) +transpose((transpose(shuffle(transpose(transpose(transpose(transpose((echo(X,4,6) |(shuffle(X) |(X+transpose(X,12) ) ) ) ,4) ,4) ,-7) ,-5) ) ,-5) +((arpeggio(shuffle((((transpose(arpeggio(X) ,4) |transpose((X+transpose(X,7) ) ,-7) ) |transpose(transpose(arpeggio(X) ,-5) ,4) ) +transpose(transpose(transpose((X|((((X+transpose(X,4) ) +transpose((X+transpose(X,12) ) ,7) ) +transpose(transpose(X,-7) ,4) ) +transpose(arpeggio(step(X,12) ) ,7) ) ) ,-5) ,4) ,7) ) ) ) +transpose(transpose((((((transpose(X,-7) +transpose(transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-5) ,7) ) |arpeggio(transpose(X,4) ) ) +transpose(transpose((X|X) ,-7) ,4) ) +transpose(transpose((transpose(X,4) +transpose(transpose(X,4) ,12) ) ,4) ,7) ) |echo(((arpeggio(shuffle(((step(X,12) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,4) ) +transpose((X+transpose(X,7) ) ,7) ) ) ) +transpose(step(transpose(X,-7) ,12) ,4) ) +transpose(((arpeggio(transpose(X,4) ) +transpose(arpeggio((X+transpose(X,12) ) ) ,7) ) +transpose(step((X+X) ,12) ,12) ) ,7) ) ,4,6) ) ,4) ,4) ) +transpose(((transpose(transpose(transpose(transpose(X,-5) ,-5) ,-5) ,4) |((shuffle(X) +transpose((X|(step(X,12) |(X+transpose(X,12) ) ) ) ,12) ) +transpose((echo(X,4,6) +transpose((transpose(X,-5) +transpose(shuffle(X) ,7) ) ,7) ) ,12) ) ) |((step(transpose(transpose((X+X) ,4) ,-7) ,12) +transpose(transpose(transpose((((X+transpose(X,7) ) +transpose((X+transpose(X,12) ) ,12) ) +transpose(X,7) ) ,4) ,-7) ,7) ) +transpose(step(step(((((transpose(X,4) +transpose((transpose(X,-7) +transpose((X+transpose(X,7) ) ,7) ) ,4) ) +transpose(shuffle(X) ,7) ) |transpose(transpose(X,4) ,4) ) |transpose((echo(echo(X,4,6) ,4,6) +transpose(arpeggio(step(X,12) ) ,12) ) ,-7) ) ,12) ,12) ,12) ) ) ,7) ) ) ,4) ) +transpose(transpose((transpose((transpose(transpose(transpose(transpose(X,4) ,-5) ,4) ,4) |(echo((X+transpose(X,12) ) ,4,6) +transpose(transpose((X+transpose(X,7) ) ,-5) ,12) ) ) ,-5) |transpose(transpose(transpose(arpeggio((X|(X|X) ) ) ,-5) ,-7) ,-7) ) ,-7) ,7) ) ) ,-5) ,4) ) +transpose(transpose((transpose(((shuffle(shuffle((step(transpose((X|((X+transpose(X,4) ) +transpose(X,7) ) ) ,-5) ,12) |shuffle(step(step(X,12) ,12) ) ) ) ) +transpose(echo((step((arpeggio(X) |(X+(X+transpose(X,12) ) ) ) ,12) +transpose(((((X+transpose(((X|X) +transpose(transpose(X,-5) ,7) ) ,4) ) +transpose(((((transpose(X,-5) +transpose(X,7) ) +transpose(transpose((X+transpose(X,7) ) ,4) ,4) ) +transpose(step(X,12) ,7) ) |transpose((X+X) ,-5) ) ,7) ) +transpose((X|((arpeggio(transpose(X,-7) ) +transpose(X,4) ) +transpose(X,7) ) ) ,4) ) +transpose(echo(((X+transpose(X,7) ) +transpose((echo(X,4,6) +X) ,7) ) ,4,6) ,7) ) ,7) ) ,4,6) ,4) ) +transpose(transpose(transpose(shuffle((((X+transpose(arpeggio(X) ,4) ) +transpose(X,7) ) |transpose(step(transpose(X,-7) ,12) ,-5) ) ) ,-7) ,-5) ,7) ) ,-7) |shuffle(((echo((((transpose(transpose(arpeggio(X) ,4) ,4) |transpose(((transpose(X,-7) |transpose(X,-7) ) +transpose(X,12) ) ,4) ) +transpose(transpose(((transpose(X,-7) +transpose(X,12) ) |arpeggio(X) ) ,4) ,12) ) +transpose(echo(transpose(((step(X,12) +transpose(transpose((arpeggio(((X+transpose(X,12) ) |((X+transpose(X,4) ) +transpose(X,7) ) ) ) |transpose(transpose(X,4) ,-7) ) ,4) ,4) ) +transpose((transpose(X,4) |transpose(X,-7) ) ,7) ) ,-5) ,4,6) ,7) ) ,4,6) +transpose(transpose(((echo(transpose(X,-5) ,4,6) +transpose(transpose(shuffle(X) ,-7) ,12) ) +transpose(shuffle(((transpose(transpose((((X+transpose(X,4) ) +transpose(X,7) ) +transpose(X,7) ) ,-7) ,-7) |(((transpose(X,4) +transpose(transpose((arpeggio(X) +transpose(echo(X,4,6) ,12) ) ,-5) ,4) ) +transpose((transpose(X,4) +echo((X|X) ,4,6) ) ,7) ) +(((step(X,12) +transpose(X,4) ) +transpose(step(transpose(X,4) ,12) ,7) ) +transpose(X,12) ) ) ) +transpose((transpose((transpose(X,4) +transpose(echo(X,4,6) ,12) ) ,-7) +transpose((((transpose(X,-5) +transpose(X,-7) ) |((X+transpose(X,7) ) |X) ) +transpose(((transpose((X|X) ,4) +transpose(echo(X,4,6) ,4) ) +transpose(echo(X,4,6) ,7) ) ,12) ) ,7) ) ,12) ) ) ,12) ) ,-7) ,4) ) +transpose((echo((transpose((step((transpose(step(X,12) ,4) |(transpose(X,-5) +transpose(arpeggio(transpose(X,-7) ) ,12) ) ) ,12) |(transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-5) +transpose(transpose(shuffle(step(X,12) ) ,-5) ,12) ) ) ,-5) |(echo((X+transpose(X,7) ) ,4,6) +transpose(transpose(X,-5) ,4) ) ) ,4,6) +transpose(transpose(transpose(arpeggio((X|X) ) ,-5) ,-5) ,-7) ) ,7) ) ) ) ,-5) ,7) ) +transpose(transpose((shuffle(((transpose(transpose((((X+transpose(X,12) ) +transpose(transpose(X,-5) ,12) ) |arpeggio(((step(X,12) |echo(X,4,6) ) +transpose((arpeggio(transpose(X,-5) ) +transpose((X+transpose(X,12) ) ,7) ) ,12) ) ) ) ,4) ,-7) +transpose((((step(transpose(transpose(((X|X) |transpose(transpose(X,-5) ,-7) ) ,-5) ,4) ,12) |transpose(arpeggio(echo(X,4,6) ) ,-7) ) +transpose((shuffle(transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,4) ) |((arpeggio(X) +(X+transpose(X,12) ) ) |transpose((echo(X,4,6) +transpose(X,7) ) ,-7) ) ) ,12) ) +transpose(((shuffle(shuffle(transpose(echo(transpose(step(X,12) ,4) ,4,6) ,-7) ) ) |((transpose(((arpeggio(X) +transpose((X+(X+transpose(X,7) ) ) ,7) ) +(arpeggio(X) +transpose((X|X) ,7) ) ) ,-5) +transpose(transpose(X,-5) ,4) ) +transpose(shuffle(((transpose(((arpeggio(X) +transpose(step(X,12) ,4) ) +transpose(X,7) ) ,4) +transpose((X|X) ,4) ) +transpose((shuffle(X) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,12) ) ,7) ) ) ,7) ) ) |transpose(transpose((transpose(transpose(echo((X+transpose(X,7) ) ,4,6) ,4) ,4) +transpose(arpeggio(((X+transpose(X,4) ) +transpose(transpose((X|X) ,-7) ,12) ) ) ,7) ) ,-5) ,-7) ) ,7) ) ,7) ) +transpose(transpose(step(arpeggio(echo((((X+transpose(X,4) ) +transpose((X+X) ,7) ) +transpose(transpose((X+transpose(X,12) ) ,-5) ,7) ) ,4,6) ) ,12) ,-5) ,4) ) ) +transpose((transpose(transpose(((shuffle((((((X+transpose(X,7) ) +transpose(X,4) ) +transpose((((X|X) +transpose((X+transpose(X,7) ) ,4) ) +transpose(echo(X,4,6) ,7) ) ,7) ) +transpose(((transpose(X,4) +X) +transpose(transpose(X,4) ,12) ) ,7) ) +transpose(shuffle(X) ,12) ) ) +transpose((step((transpose(X,4) +transpose((transpose(X,-7) +transpose(X,12) ) ,7) ) ,12) |transpose(transpose((transpose(X,4) |X) ,-5) ,-5) ) ,4) ) +transpose(((transpose(X,-5) +transpose((X+transpose((X+transpose(X,7) ) ,12) ) ,4) ) +transpose(((echo(X,4,6) +transpose(X,12) ) |step(transpose(X,-5) ,12) ) ,7) ) ,7) ) ,-5) ,-7) |transpose(transpose(transpose((arpeggio(X) +transpose(step((X|X) ,12) ,12) ) ,4) ,-5) ,4) ) ,4) ) ,4) ,4) ) +transpose(transpose(arpeggio(((transpose((((((transpose(X,-5) +transpose(((transpose(X,-7) +transpose(X,7) ) |transpose((X+transpose(X,7) ) ,-7) ) ,7) ) +transpose((transpose(X,-5) +transpose(echo((X|X) ,4,6) ,12) ) ,7) ) +transpose((echo(transpose(echo((X|X) ,4,6) ,-7) ,4,6) +transpose(transpose((transpose(X,-7) +transpose((X+X) ,12) ) ,-7) ,12) ) ,12) ) +transpose(((step(step((transpose(X,-5) +transpose((X+X) ,12) ) ,12) ,12) |transpose(echo((step(X,12) +transpose((X+X) ,7) ) ,4,6) ,-7) ) +transpose((transpose(transpose(transpose(X,4) ,4) ,4) |transpose((arpeggio(X) |echo(transpose(X,4) ,4,6) ) ,4) ) ,7) ) ,4) ) |((transpose(transpose(step((X+transpose(X,7) ) ,12) ,-7) ,4) +transpose(transpose(shuffle(transpose(transpose((step(X,12) +transpose(X,7) ) ,-5) ,-5) ) ,-7) ,4) ) +transpose((((shuffle(transpose(transpose(transpose(shuffle(X) ,-5) ,4) ,-5) ) +transpose(echo(((transpose((X|X) ,-5) |echo(X,4,6) ) |arpeggio(X) ) ,4,6) ,4) ) +transpose((echo(transpose(transpose(echo((X+transpose(X,12) ) ,4,6) ,4) ,-5) ,4,6) |(((((step(X,12) +transpose(X,12) ) +transpose((transpose(X,-7) +transpose(X,7) ) ,4) ) +transpose((X|transpose(X,4) ) ,7) ) +((arpeggio(X) +transpose(transpose(X,-7) ,7) ) +transpose(X,12) ) ) |arpeggio(transpose((echo(X,4,6) +transpose((X|X) ,7) ) ,-5) ) ) ) ,7) ) +transpose(step(transpose((X+transpose((X+X) ,12) ) ,-5) ,12) ,12) ) ,7) ) ) ,4) +transpose(step(transpose(transpose(((((transpose(((echo(((X|X) +(X|X) ) ,4,6) +transpose(arpeggio((X|X) ) ,4) ) +transpose(arpeggio(echo(X,4,6) ) ,7) ) ,4) +transpose(shuffle(shuffle(step(X,12) ) ) ,4) ) +transpose(echo(shuffle((X+transpose(shuffle(X) ,7) ) ) ,4,6) ,7) ) +transpose(transpose(((X+transpose(X,12) ) |X) ,-5) ,7) ) +transpose(shuffle(transpose(transpose(((step(X,12) +transpose(((X|X) |step(X,12) ) ,12) ) +transpose((shuffle(X) |X) ,7) ) ,-5) ,-5) ) ,7) ) ,4) ,4) ,12) ,4) ) +transpose(step(transpose(step(transpose(transpose(X,-7) ,-5) ,12) ,4) ,12) ,7) ) ) ,-7) ,7) )
random seed used was 120394586

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