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(transpose((step(arpeggio(X) ,12) +transpose(transpose((X|X) ,4) ,12) ) ,4) ,-7) +transpose(step((((transpose(X,4) +transpose(X,7) ) |X) +transpose(step(transpose((X|X) ,-7) ,12) ,12) ) ,12) ,-7) ) +transpose(((((transpose((X|X) ,-7) |shuffle(transpose((transpose(step((X+transpose(X,7) ) ,12) ,4) +transpose(X,12) ) ,-5) ) ) |((arpeggio(((arpeggio(X) +transpose(X,12) ) |X) ) +transpose(transpose(echo(transpose((X+transpose(shuffle(X) ,7) ) ,-5) ,4,6) ,-7) ,4) ) +transpose(((step(((transpose(X,4) +transpose((X+(X+transpose(X,12) ) ) ,4) ) +transpose(X,7) ) ,12) +transpose(echo(transpose(X,-7) ,4,6) ,4) ) +transpose(arpeggio(X) ,7) ) ,7) ) ) +transpose(transpose(transpose(arpeggio(X) ,-7) ,-5) ,4) ) +transpose(transpose(transpose(((((step(X,12) +transpose((X+transpose(X,7) ) ,4) ) +transpose(X,7) ) |echo(X,4,6) ) |(transpose(transpose(X,-5) ,-7) |(transpose(X,-5) +transpose(arpeggio((X|X) ) ,12) ) ) ) ,4) ,-5) ,7) ) ,7) ) ,-7) |(((arpeggio(transpose(shuffle(arpeggio(transpose((((step(echo((X+transpose(X,12) ) ,4,6) ,12) +transpose(transpose((transpose(X,-7) |transpose(X,-5) ) ,-5) ,7) ) |transpose(arpeggio((X+transpose(X,7) ) ) ,-5) ) |transpose(transpose(transpose((step(transpose(X,4) ,12) +((X+transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,4) ) +transpose(arpeggio(X) ,7) ) ) ,-7) ,-7) ,4) ) ,4) ) ) ,-7) ) +transpose((echo((transpose((transpose(((transpose(arpeggio(((X+transpose(X,4) ) +transpose(X,7) ) ) ,4) +transpose((transpose(((X+transpose(transpose(X,4) ,4) ) +transpose(X,7) ) ,-5) +transpose(transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-5) ,12) ) ,12) ) +transpose(((((X|X) |X) +transpose(transpose((transpose(X,4) |echo(X,4,6) ) ,-5) ,7) ) +transpose(transpose(echo(echo(X,4,6) ,4,6) ,-7) ,12) ) ,12) ) ,-5) |step(step(shuffle(transpose(echo((X+transpose(X,12) ) ,4,6) ,-7) ) ,12) ,12) ) ,-5) |transpose(step((step(transpose((transpose(X,-5) |X) ,-5) ,12) +(transpose((((transpose(transpose(X,-7) ,-5) +(transpose(X,-5) +transpose(X,12) ) ) +transpose(((X+transpose(X,7) ) +transpose(shuffle(X) ,7) ) ,4) ) +transpose(echo(step((X+transpose(X,7) ) ,12) ,4,6) ,7) ) ,-5) +transpose(((X+transpose(X,7) ) |transpose(transpose(X,-5) ,-5) ) ,7) ) ) ,12) ,4) ) ,4,6) +(shuffle(shuffle(transpose(transpose((((transpose(X,-7) +transpose((X+X) ,4) ) +transpose((X+transpose((X+transpose(X,12) ) ,12) ) ,7) ) |(X+transpose(X,7) ) ) ,-7) ,4) ) ) +transpose(transpose(shuffle(transpose((transpose(transpose(shuffle(arpeggio(transpose(X,4) ) ) ,4) ,-7) +transpose(transpose(shuffle(shuffle((((X+transpose(X,4) ) +transpose(X,7) ) +step(X,12) ) ) ) ,4) ,7) ) ,4) ) ,-5) ,7) ) ) ,7) ) +transpose(transpose(shuffle((transpose((transpose((transpose((transpose((transpose((arpeggio(shuffle(arpeggio(X) ) ) +transpose(transpose(X,4) ,4) ) ,4) +arpeggio(((echo(X,4,6) |((X|X) +transpose((X+transpose(X,12) ) ,7) ) ) +transpose(transpose((X+transpose(transpose(X,-7) ,12) ) ,-5) ,7) ) ) ) ,-7) |echo((X|transpose(transpose((X|(X+transpose(X,7) ) ) ,-7) ,-7) ) ,4,6) ) ,-7) +transpose(arpeggio(transpose(transpose(arpeggio((X+transpose(X,7) ) ) ,-5) ,4) ) ,12) ) ,4) +transpose((arpeggio(transpose((((transpose((X|(X+transpose(X,12) ) ) ,-7) +transpose(step(transpose(X,-5) ,12) ,7) ) +transpose(shuffle(transpose((X+X) ,-5) ) ,12) ) |transpose(transpose((X+X) ,4) ,-7) ) ,-7) ) +transpose((((transpose((transpose((transpose((X+transpose(X,7) ) ,-5) +transpose(transpose(((X+transpose(X,7) ) +transpose(transpose(X,-7) ,7) ) ,-7) ,12) ) ,-7) +transpose(transpose((echo((X|X) ,4,6) |((transpose((X+transpose(X,12) ) ,4) +transpose(transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,4) ,4) ) +transpose(step((X+transpose(X,7) ) ,12) ,7) ) ) ,4) ,12) ) ,4) |(((((X+transpose(step(X,12) ,12) ) +transpose(((X+transpose(X,7) ) +echo(X,4,6) ) ,7) ) +transpose(arpeggio((transpose(arpeggio(((X+transpose(X,4) ) +transpose(X,7) ) ) ,-5) +transpose(((transpose(X,-7) +transpose((X|X) ,4) ) +transpose(X,7) ) ,7) ) ) ,4) ) +transpose((((shuffle(X) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,12) ) +transpose((transpose((X|X) ,-5) +transpose(transpose(X,-5) ,7) ) ,12) ) |transpose((X+transpose(X,12) ) ,4) ) ,7) ) |shuffle((transpose(X,4) |step(transpose(X,-5) ,12) ) ) ) ) +transpose((transpose(transpose(transpose(X,-7) ,-7) ,-5) |echo(transpose(X,-7) ,4,6) ) ,7) ) |(step(transpose(transpose((shuffle(X) +transpose((step(X,12) +((X+transpose(X,7) ) +echo(X,4,6) ) ) ,12) ) ,4) ,4) ,12) +transpose(transpose(transpose(transpose(((arpeggio(X) +transpose((X|X) ,4) ) +transpose(transpose(X,4) ,7) ) ,4) ,4) ,-5) ,-7) ) ) ,7) ) ,7) ) ,-5) +transpose(((transpose(step(((step(((X+X) +transpose(transpose(X,4) ,7) ) ,12) +transpose((X+transpose(transpose(X,-7) ,12) ) ,7) ) +shuffle(transpose(arpeggio(X) ,4) ) ) ,12) ,-7) |(transpose(echo((((X+transpose(X,12) ) +transpose(transpose(X,4) ,7) ) +((X+transpose(X,4) ) +transpose(transpose(X,-5) ,7) ) ) ,4,6) ,4) +(transpose((((transpose(X,-7) +transpose(shuffle(X) ,4) ) +transpose(transpose(X,-5) ,7) ) +transpose(shuffle(arpeggio(step(X,12) ) ) ,7) ) ,4) +transpose(transpose(transpose(transpose(step(arpeggio(echo(X,4,6) ) ,12) ,-7) ,-5) ,-5) ,7) ) ) ) +transpose(transpose((arpeggio(transpose(step(transpose(transpose(transpose(shuffle(step(X,12) ) ,-7) ,-5) ,4) ,12) ,-5) ) |transpose((shuffle(arpeggio(transpose((X+transpose(X,12) ) ,-7) ) ) |((transpose((X+X) ,-5) |shuffle(X) ) |step(step(((X+transpose(X,4) ) +transpose(transpose(X,-5) ,7) ) ,12) ,12) ) ) ,-7) ) ,-7) ,12) ) ,4) ) ) ,-5) ,4) ) +transpose(((transpose(transpose(step(echo((((transpose(((transpose(X,-5) +transpose(X,4) ) +transpose(transpose(X,4) ,7) ) ,4) |transpose((X+transpose(transpose(X,4) ,12) ) ,4) ) +transpose((step((((X+transpose(X,7) ) +transpose(X,4) ) +transpose(X,7) ) ,12) +transpose(X,-5) ) ,7) ) +transpose(step(step(step(shuffle(((X+transpose(X,4) ) +transpose(X,7) ) ) ,12) ,12) ,12) ,-7) ) ,4,6) ,12) ,-7) ,-7) |transpose(((transpose((echo(echo(transpose(X,-7) ,4,6) ,4,6) +(transpose(transpose((X|X) ,4) ,-5) +((X+X) |X) ) ) ,4) +transpose((((((X|((X+transpose(X,4) ) +transpose(X,7) ) ) |transpose((X+transpose(shuffle(X) ,12) ) ,-7) ) +transpose(echo(step(transpose((X+transpose(X,12) ) ,-7) ,12) ,4,6) ,4) ) +((echo(transpose(transpose((X+transpose(X,7) ) ,-7) ,-7) ,4,6) +(transpose(((X|X) |(((echo(X,4,6) +transpose(transpose(X,4) ,4) ) +transpose(X,7) ) |(shuffle(X) +transpose(X,7) ) ) ) ,-5) +transpose(arpeggio(arpeggio((X+transpose((X+transpose(X,12) ) ,7) ) ) ) ,7) ) ) +transpose((transpose(transpose(transpose((X+X) ,-7) ,4) ,-7) |transpose(echo(transpose(X,-5) ,4,6) ,4) ) ,7) ) ) |arpeggio(echo((transpose(transpose((X+transpose(X,12) ) ,-7) ,-5) +transpose((((X+transpose(X,4) ) +transpose((X+transpose(X,12) ) ,7) ) +transpose(transpose((arpeggio(X) |X) ,-7) ,12) ) ,7) ) ,4,6) ) ) ,4) ) +transpose(((step(step((shuffle((shuffle(X) +transpose(X,12) ) ) +transpose((((X+transpose(X,12) ) +transpose((X|X) ,4) ) +transpose((((X+transpose(X,4) ) +transpose(X,7) ) +transpose(transpose(X,4) ,7) ) ,7) ) ,7) ) ,12) ,12) +transpose(shuffle(shuffle(shuffle((X+transpose((X+transpose(X,7) ) ,12) ) ) ) ) ,4) ) +transpose((transpose(((transpose(transpose(transpose(X,-7) ,-7) ,4) |arpeggio(X) ) +transpose(transpose(((transpose(X,-5) +transpose(arpeggio(X) ,4) ) +transpose(transpose(X,4) ,7) ) ,4) ,7) ) ,4) |transpose(((X+transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,12) ) +transpose(transpose(transpose(X,-5) ,-5) ,7) ) ,-5) ) ,7) ) ,7) ) ,4) ) +transpose((((transpose((transpose(((shuffle(transpose(transpose(X,4) ,-5) ) +transpose(arpeggio(transpose(transpose(step(X,12) ,4) ,-7) ) ,12) ) +transpose(transpose(step(arpeggio(transpose(echo(X,4,6) ,-5) ) ,12) ,-5) ,12) ) ,-7) |(transpose((((X+transpose(X,12) ) +transpose((X|X) ,12) ) +transpose(X,-5) ) ,-7) +transpose(((((X+transpose(X,7) ) |step(X,12) ) +transpose(transpose((X|shuffle(X) ) ,4) ,12) ) +transpose(shuffle(((step(X,12) +transpose(X,12) ) |shuffle((X+transpose(X,12) ) ) ) ) ,4) ) ,12) ) ) ,-5) +shuffle(transpose(transpose(((shuffle((((((X+transpose(X,4) ) +transpose(X,7) ) |((X+transpose(X,12) ) +transpose((X|X) ,12) ) ) +transpose(transpose((((X+transpose(X,4) ) +transpose(X,7) ) |arpeggio(X) ) ,-5) ,7) ) +transpose((X+transpose(transpose(transpose(X,4) ,4) ,12) ) ,12) ) ) +transpose((transpose((X+transpose((transpose(X,-5) +transpose(X,4) ) ,7) ) ,-5) |(((X+transpose(X,7) ) +transpose(X,4) ) +transpose(X,7) ) ) ,4) ) +transpose(transpose(((arpeggio(X) +transpose(transpose(((((transpose(X,4) +transpose(transpose(echo(X,4,6) ,4) ,4) ) +transpose(X,7) ) +transpose(transpose(((X|X) +transpose(X,12) ) ,4) ,4) ) +transpose(transpose(transpose((X|X) ,4) ,-5) ,7) ) ,4) ,4) ) +transpose(((arpeggio(transpose(X,-7) ) +transpose(echo((X|X) ,4,6) ,7) ) |echo(((transpose(X,4) +transpose(((X+transpose(X,12) ) +transpose(X,12) ) ,4) ) +transpose(echo(((X+transpose(X,4) ) +transpose((X|X) ,7) ) ,4,6) ,7) ) ,4,6) ) ,7) ) ,4) ,7) ) ,4) ,-7) ) ) +transpose((transpose((transpose((transpose((transpose(echo(X,4,6) ,-7) +transpose(transpose(arpeggio(X) ,-7) ,7) ) ,4) |echo(step(X,12) ,4,6) ) ,-5) +transpose(transpose(step(arpeggio(transpose(X,-7) ) ,12) ,-7) ,12) ) ,-7) +transpose(transpose(transpose(transpose(echo(((X|X) +transpose(transpose(X,-5) ,12) ) ,4,6) ,-7) ,-7) ,-7) ,7) ) ,4) ) +transpose(transpose(transpose((((((X+transpose(arpeggio(shuffle(X) ) ,7) ) +transpose(step(transpose(transpose(X,-7) ,-7) ,12) ,7) ) +transpose(transpose(transpose(((X+transpose(X,7) ) +transpose((X+X) ,7) ) ,-5) ,-5) ,4) ) +transpose(transpose((((transpose(X,4) |transpose(X,-5) ) +transpose(shuffle(transpose(X,-7) ) ,4) ) +transpose(X,7) ) ,-7) ,7) ) |transpose(step(((transpose(transpose((transpose(X,4) +step(X,12) ) ,4) ,4) +transpose(transpose(X,4) ,12) ) +transpose(echo(echo(((X|X) +X) ,4,6) ,4,6) ,12) ) ,12) ,4) ) ,-5) ,4) ,7) ) ,7) ) ,7) ) )
random seed used was 238988327

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