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:
((((((((echo(echo(transpose((X+X) ,-7) ,4,6) ,4,6) +transpose(shuffle(echo((X|X) ,4,6) ) ,7) ) +(transpose(transpose(((transpose(X,4) +X) +((transpose(X,4) +transpose(X,4) ) +transpose(arpeggio(X) ,7) ) ) ,-7) ,4) +transpose((transpose(shuffle(arpeggio(transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-7) ) ) ,4) +transpose((transpose((((X+transpose(X,12) ) +transpose((X+transpose(X,12) ) ,12) ) +transpose(step(X,12) ,12) ) ,4) +transpose(echo(transpose(X,4) ,4,6) ,7) ) ,12) ) ,7) ) ) +transpose(shuffle(transpose(transpose((transpose((X+transpose(transpose(X,-7) ,7) ) ,-7) +((X+X) +(((X+transpose(X,4) ) +transpose(X,7) ) |X) ) ) ,-5) ,-7) ) ,4) ) +transpose(transpose(echo(transpose(((transpose(X,-7) |transpose((X+X) ,4) ) |transpose(transpose(shuffle(X) ,-5) ,-7) ) ,4) ,4,6) ,-5) ,7) ) +transpose(transpose((transpose(transpose(step((transpose(transpose((X+transpose(X,12) ) ,-5) ,-7) |(transpose(X,-7) +transpose(((X|X) +((X+transpose((X+transpose(X,7) ) ,4) ) +transpose(transpose(X,4) ,7) ) ) ,7) ) ) ,12) ,4) ,4) +step(transpose(echo(shuffle(X) ,4,6) ,4) ,12) ) ,-7) ,7) ) |((shuffle(step(((shuffle((X+X) ) +transpose(((X+transpose(X,12) ) +transpose(step(X,12) ,12) ) ,7) ) +(shuffle((X+X) ) |transpose(X,4) ) ) ,12) ) +transpose(step((((arpeggio((X|X) ) |(X|X) ) +transpose(transpose((X+transpose((X|X) ,-5) ) ,-7) ,7) ) +echo(shuffle(transpose(X,-5) ) ,4,6) ) ,12) ,12) ) |arpeggio(transpose(transpose(transpose(((X+transpose(X,12) ) +transpose((shuffle((X+X) ) +(shuffle(X) |X) ) ,7) ) ,4) ,4) ,-7) ) ) ) |transpose((transpose(((step(transpose(transpose(((shuffle((X|X) ) |transpose((X|echo(X,4,6) ) ,-7) ) +((step(shuffle(echo(X,4,6) ) ,12) |((X+transpose(X,12) ) +transpose(transpose(X,4) ,12) ) ) +transpose(echo(shuffle(X) ,4,6) ,4) ) ) ,4) ,-5) ,12) +transpose(step((transpose(((shuffle(((X+transpose(X,12) ) |echo(X,4,6) ) ) +transpose(echo(X,4,6) ,4) ) +transpose(((((X+transpose(X,4) ) +transpose(X,7) ) +transpose(X,7) ) +X) ,7) ) ,-7) +transpose(arpeggio(transpose(transpose((transpose(((X+X) |X) ,-7) +shuffle((X+X) ) ) ,4) ,-5) ) ,12) ) ,12) ,4) ) +transpose((transpose(transpose(transpose(transpose(transpose(echo((X+transpose((step(X,12) +transpose(transpose(X,-5) ,12) ) ,7) ) ,4,6) ,-5) ,-7) ,4) ,-7) ,-7) +transpose(shuffle(((transpose(transpose(X,4) ,-5) +(arpeggio(shuffle(X) ) +shuffle((X+X) ) ) ) +(shuffle(transpose(X,-5) ) |(transpose((shuffle(arpeggio(X) ) +transpose(((X+transpose(X,-7) ) +(((X+transpose(X,4) ) +transpose(X,7) ) +transpose((X+transpose(X,12) ) ,12) ) ) ,12) ) ,-7) |transpose(transpose(transpose(transpose(transpose(transpose(X,4) ,-7) ,4) ,4) ,-5) ,-5) ) ) ) ) ,12) ) ,7) ) ,-5) |step(((((transpose(shuffle(X) ,-7) +transpose(((X+transpose((X|X) ,12) ) +(X+transpose(X,7) ) ) ,12) ) +transpose(((transpose(((X+transpose(X,4) ) +transpose(transpose(X,-5) ,7) ) ,4) +((transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,4) +transpose(X,4) ) +transpose((X+X) ,7) ) ) +transpose(echo(echo(X,4,6) ,4,6) ,7) ) ,-5) ) |(transpose((transpose(transpose(X,4) ,-7) |(X+transpose(X,12) ) ) ,4) +transpose(step(transpose(X,4) ,12) ,7) ) ) +transpose(arpeggio((transpose(X,-7) +transpose((((X+X) +(X|X) ) +transpose(transpose(shuffle(X) ,-5) ,12) ) ,12) ) ) ,-7) ) ,12) ) ,4) ) +transpose(((step(((transpose(echo(((step((X+X) ,12) +transpose(X,4) ) +transpose(transpose(transpose(X,4) ,-7) ,7) ) ,4,6) ,-5) +transpose(transpose(((X+transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,7) ) +transpose(transpose(X,-5) ,12) ) ,4) ,12) ) |transpose(((step(X,12) +transpose(X,4) ) +transpose(((((X+transpose(X,12) ) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,12) ) +(transpose(X,-7) +transpose(X,12) ) ) +transpose(echo(transpose(X,4) ,4,6) ,7) ) ,7) ) ,4) ) ,12) +(((transpose((((transpose((transpose(X,-5) +transpose((((X+transpose(X,4) ) +transpose(X,7) ) +transpose(echo(X,4,6) ,7) ) ,7) ) ,-7) |step(transpose(X,-5) ,12) ) |echo(arpeggio(echo(X,4,6) ) ,4,6) ) |((((X+transpose(transpose(X,-5) ,12) ) +transpose(echo(X,4,6) ,12) ) +((transpose(((X+transpose(X,12) ) +X) ,-7) |step(transpose(X,4) ,12) ) +transpose(transpose(((transpose(arpeggio(X) ,4) +transpose(transpose(X,-5) ,4) ) +transpose(((shuffle(X) +transpose((X+X) ,4) ) +transpose(X,7) ) ,7) ) ,-7) ,7) ) ) +transpose((arpeggio(arpeggio(shuffle(X) ) ) +transpose(transpose(transpose(transpose(X,-5) ,-7) ,-5) ,7) ) ,12) ) ) ,4) +(((transpose(X,-7) +transpose(transpose(transpose(X,4) ,-7) ,4) ) +transpose(arpeggio(X) ,7) ) +transpose((((step((X+transpose(X,12) ) ,12) +transpose(arpeggio(X) ,12) ) +transpose((transpose(transpose(transpose(X,4) ,4) ,-5) +transpose(transpose(X,-5) ,-5) ) ,7) ) |shuffle(shuffle(transpose(transpose(X,-7) ,4) ) ) ) ,12) ) ) +transpose(((arpeggio(transpose((step(echo(((((((X|X) +((X+transpose(X,4) ) +transpose(X,7) ) ) +transpose(step(X,12) ,12) ) +transpose(step((X|(X+transpose(X,12) ) ) ,12) ,4) ) +transpose(echo(((X+X) |echo(transpose(X,4) ,4,6) ) ,4,6) ,7) ) +transpose((((X+transpose(X,4) ) +transpose(X,7) ) +((((X+X) +transpose(X,7) ) +transpose((X+transpose(X,12) ) ,4) ) +transpose((X+X) ,7) ) ) ,-5) ) ,4,6) ,12) +transpose((transpose((transpose(shuffle(((X+transpose((X+transpose((X|X) ,7) ) ,4) ) +transpose(transpose(X,-5) ,7) ) ) ,-7) +(((transpose(echo(X,4,6) ,4) +transpose(X,4) ) +transpose((((X+transpose(X,4) ) +transpose(X,7) ) |transpose(X,-7) ) ,7) ) +transpose(transpose(((X+(X|X) ) +transpose((X+X) ,7) ) ,-7) ,7) ) ) ,-5) +transpose(shuffle(transpose((step(X,12) |X) ,4) ) ,12) ) ,7) ) ,-5) ) +transpose(((((transpose(X,-5) +transpose(arpeggio(step(transpose(step(arpeggio(X) ,12) ,4) ,12) ) ,7) ) |shuffle(transpose(X,-5) ) ) +transpose(transpose(echo(((arpeggio(transpose(transpose(((X+arpeggio(X) ) +transpose(transpose(X,-7) ,12) ) ,4) ,-5) ) +transpose(echo((((((X+transpose(X,12) ) |transpose(X,-7) ) +transpose(transpose((transpose(X,-7) +echo(X,4,6) ) ,-5) ,4) ) +transpose((X+transpose(X,12) ) ,7) ) |(transpose((X+transpose(X,12) ) ,-7) +((X+(X+X) ) |step(shuffle(X) ,12) ) ) ) ,4,6) ,4) ) +transpose(echo(((step(X,12) +transpose(((X|X) |arpeggio(X) ) ,4) ) +transpose((X+transpose(X,12) ) ,7) ) ,4,6) ,7) ) ,4,6) ,-7) ,12) ) +transpose(shuffle(transpose(transpose(transpose(transpose(shuffle(step((X+transpose(X,12) ) ,12) ) ,4) ,-5) ,-7) ,4) ) ,12) ) ,4) ) +transpose(((shuffle(step((transpose((((transpose(shuffle(X) ,4) |transpose(echo(X,4,6) ,-5) ) +transpose(transpose(transpose(X,-7) ,-5) ,4) ) +transpose(arpeggio(echo(X,4,6) ) ,7) ) ,-7) +transpose(transpose((transpose((X|(X+transpose(X,7) ) ) ,-7) |(transpose((X|X) ,4) +transpose(transpose(transpose(X,-7) ,-7) ,7) ) ) ,4) ,7) ) ,12) ) +transpose(transpose((((transpose(transpose(transpose(X,4) ,-5) ,4) +transpose((transpose(X,-7) +X) ,12) ) +transpose(arpeggio(X) ,12) ) |(arpeggio(transpose(X,-5) ) +transpose((((X+X) |step(X,12) ) +transpose(transpose((X+X) ,-5) ,12) ) ,12) ) ) ,-5) ,4) ) +transpose(arpeggio(echo(((transpose(transpose(((shuffle(transpose(X,-7) ) +transpose(((X+X) |echo(X,4,6) ) ,4) ) +transpose(transpose(X,-7) ,7) ) ,4) ,-7) +transpose(transpose(((X+transpose(transpose(X,-5) ,7) ) +transpose((transpose(X,4) +shuffle(X) ) ,12) ) ,-7) ,12) ) |(((transpose(arpeggio(transpose(X,-5) ) ,-7) +transpose(echo(X,4,6) ,-7) ) +transpose((((X+transpose(X,4) ) +transpose(X,7) ) |step(((X+transpose(X,4) ) +transpose(X,7) ) ,12) ) ,4) ) +transpose((transpose(shuffle((X+transpose((X+transpose(X,12) ) ,7) ) ) ,4) +((X|X) +X) ) ,7) ) ) ,4,6) ) ,7) ) ,7) ) ,4) ) +transpose((transpose((transpose(((((transpose((X|X) ,-5) +transpose(step(((X|X) +transpose((X+transpose(X,12) ) ,7) ) ,12) ,4) ) +transpose(((transpose(X,-7) +(X|X) ) |((X+X) +X) ) ,7) ) +(((X+X) +transpose(X,4) ) +transpose(X,7) ) ) +echo(transpose(X,-5) ,4,6) ) ,-7) |echo(transpose((transpose((((X+transpose(X,7) ) +transpose(X,4) ) +transpose((X+X) ,7) ) ,-5) |(shuffle(echo(X,4,6) ) |echo(((shuffle((X+transpose(X,12) ) ) +transpose(((X+transpose(X,12) ) +transpose(X,4) ) ,4) ) +transpose((X+transpose(shuffle(X) ,7) ) ,7) ) ,4,6) ) ) ,-5) ,4,6) ) ,-7) +transpose(shuffle((step(transpose((((((X+transpose(X,12) ) +transpose(echo(X,4,6) ,12) ) +transpose(transpose(X,4) ,4) ) |transpose(transpose(echo((X|X) ,4,6) ,4) ,4) ) +transpose(X,12) ) ,4) ,12) +transpose(((echo(transpose(step(step((X+transpose(X,12) ) ,12) ,12) ,-5) ,4,6) +transpose((arpeggio(arpeggio((echo(X,4,6) +transpose(X,-5) ) ) ) +transpose((echo((shuffle((X+X) ) +transpose(transpose(transpose(X,4) ,-7) ,7) ) ,4,6) |echo(shuffle(echo((transpose(X,-5) +shuffle(X) ) ,4,6) ) ,4,6) ) ,7) ) ,7) ) |step((transpose(X,-7) +transpose((((X|X) +transpose(X,-7) ) +transpose(transpose(X,-5) ,4) ) ,12) ) ,12) ) ,7) ) ) ,7) ) ,7) ) ) +transpose((transpose((transpose(step(arpeggio(transpose(transpose(X,-5) ,4) ) ,12) ,-7) |(shuffle(((((transpose((((X+transpose(X,12) ) +transpose(step(transpose(X,-7) ,12) ,4) ) +transpose(transpose(transpose(step(transpose(X,-5) ,12) ,-5) ,-5) ,7) ) ,4) |((echo(echo(transpose(X,-7) ,4,6) ,4,6) +transpose(X,12) ) +transpose(arpeggio(step((transpose(X,-7) +X) ,12) ) ,7) ) ) +(((X+transpose((X+transpose(X,12) ) ,4) ) +transpose(X,7) ) +transpose(echo(((X+transpose(X,4) ) +transpose(X,7) ) ,4,6) ,12) ) ) |(transpose(transpose(transpose(X,4) ,4) ,4) |(step(transpose(transpose(X,4) ,-7) ,12) +transpose(((transpose(X,-5) +transpose((step(X,12) |X) ,7) ) +transpose((transpose(X,4) +transpose(X,4) ) ,7) ) ,7) ) ) ) +((shuffle((transpose(arpeggio(step(echo(X,4,6) ,12) ) ,-7) +transpose((transpose(X,-5) +((X|X) +transpose((X+X) ,12) ) ) ,7) ) ) +transpose(((transpose(X,-7) +transpose(X,-7) ) |(echo(transpose(X,-5) ,4,6) +(X+transpose(((X+transpose(shuffle(X) ,4) ) +transpose(transpose(X,-5) ,7) ) ,12) ) ) ) ,4) ) +transpose(transpose(((((transpose(X,4) +transpose(X,7) ) +transpose(((X+X) |X) ,4) ) +transpose(echo(step((X+X) ,12) ,4,6) ,7) ) +transpose(transpose(echo(arpeggio(shuffle(transpose(X,4) ) ) ,4,6) ,-7) ,7) ) ,4) ,7) ) ) ) +transpose((arpeggio(arpeggio(echo(transpose(transpose(X,-7) ,4) ,4,6) ) ) +shuffle(transpose(transpose(((((transpose(X,-7) +transpose((X|X) ,4) ) +transpose(X,7) ) +(transpose(X,-5) |(X+transpose(X,7) ) ) ) +(((X+X) +transpose(X,4) ) +transpose(X,7) ) ) ,-7) ,4) ) ) ,12) ) ) ,-5) +echo(echo((((((arpeggio(transpose(transpose(X,-7) ,-7) ) |((X+X) +echo(transpose(X,4) ,4,6) ) ) +transpose(echo(transpose(transpose(X,4) ,-5) ,4,6) ,4) ) +transpose((((step(transpose(transpose((X|X) ,4) ,4) ,12) +transpose(((X+transpose(X,4) ) +transpose((X+transpose(X,7) ) ,7) ) ,12) ) +transpose(echo(arpeggio(X) ,4,6) ,4) ) +transpose(transpose(shuffle(step(((X+X) |X) ,12) ) ,-7) ,7) ) ,7) ) +step(((shuffle(X) +transpose(X,4) ) +transpose(transpose(echo(X,4,6) ,4) ,7) ) ,12) ) |(transpose(transpose(transpose((((X+transpose(X,4) ) +transpose(X,7) ) +(X|X) ) ,-7) ,4) ,4) +(step(shuffle((X+transpose(transpose(X,4) ,12) ) ) ,12) +transpose(transpose(transpose(transpose(X,-5) ,-5) ,-7) ,-7) ) ) ) ,4,6) ,4,6) ) ,7) ) ,-7) )
random seed used was 2532808

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