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((X|X) ,-5) +transpose(((X|X) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,12) ) ,4) ) +transpose(transpose(((X+transpose((X|X) ,4) ) +transpose((X|X) ,7) ) ,-5) ,7) ) +step(arpeggio((X+transpose(X,12) ) ) ,12) ) +transpose(shuffle((arpeggio(X) +transpose(transpose(echo((X+X) ,4,6) ,-7) ,12) ) ) ,12) ) +transpose(transpose(echo(transpose(transpose((((shuffle(transpose(X,4) ) +transpose(transpose(step(X,12) ,4) ,4) ) +transpose(transpose(transpose(X,-7) ,-7) ,7) ) +transpose(shuffle((transpose(X,-7) |step(transpose(X,-7) ,12) ) ) ,7) ) ,-7) ,4) ,4,6) ,-5) ,7) ) ,-7) +(transpose(shuffle(step((transpose(transpose((transpose(arpeggio(transpose((((X|X) +transpose(transpose(transpose(X,-5) ,-7) ,4) ) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,7) ) ,-5) ) ,4) |arpeggio(transpose((transpose(step(X,12) ,4) +(transpose(X,4) +(X+X) ) ) ,4) ) ) ,-5) ,4) |transpose((transpose((transpose(echo(X,4,6) ,-7) +transpose((X+transpose(X,12) ) ,7) ) ,-5) +transpose(echo((transpose((X|(shuffle(X) |transpose(X,4) ) ) ,4) |transpose(transpose(arpeggio(echo(X,4,6) ) ,-5) ,4) ) ,4,6) ,7) ) ,-7) ) ,12) ) ,-7) |((((transpose(((((transpose(transpose(X,4) ,4) +transpose(X,4) ) +transpose((((transpose(X,4) +transpose(transpose(X,-5) ,4) ) +transpose(shuffle(X) ,7) ) |X) ,7) ) +transpose((step(((X+transpose(X,4) ) +transpose(X,7) ) ,12) |(transpose(X,4) +transpose(X,7) ) ) ,7) ) |transpose(transpose(((transpose(X,-5) |transpose(X,4) ) +transpose(transpose((shuffle(X) +transpose(step(X,12) ,7) ) ,-7) ,7) ) ,-7) ,-7) ) ,4) +transpose((transpose((transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-5) |((transpose(X,-5) |echo(X,4,6) ) +transpose(X,7) ) ) ,-5) +transpose(((step((X+(X+transpose(X,12) ) ) ,12) |echo((arpeggio(X) +transpose(X,12) ) ,4,6) ) |echo((((X+transpose(X,7) ) +transpose(step(X,12) ,4) ) +transpose(((X+transpose(X,7) ) +transpose(X,-7) ) ,7) ) ,4,6) ) ,-7) ) ,-5) ) +transpose((((echo((transpose(X,4) +transpose((X+transpose(X,12) ) ,4) ) ,4,6) +transpose(((transpose(X,4) |X) +transpose(transpose(X,-7) ,7) ) ,-7) ) +(arpeggio(arpeggio((transpose(X,4) |X) ) ) +transpose((transpose(transpose(X,-5) ,-5) +transpose((transpose(X,4) |(shuffle(X) +transpose((X+transpose(X,12) ) ,12) ) ) ,7) ) ,-5) ) ) +transpose(transpose(transpose((((X+X) +transpose(transpose(X,4) ,4) ) +transpose(transpose(X,-5) ,7) ) ,-7) ,4) ,7) ) ,-7) ) |transpose(((transpose((((((X+X) +transpose((transpose(X,4) +transpose((X+transpose(X,7) ) ,12) ) ,4) ) +transpose(transpose(X,-7) ,7) ) +transpose(shuffle(echo(transpose((X+transpose(transpose(X,4) ,7) ) ,-5) ,4,6) ) ,4) ) +transpose((echo(shuffle(transpose(shuffle(X) ,-5) ) ,4,6) +transpose(((X+transpose(X,4) ) +transpose(echo((X+X) ,4,6) ,7) ) ,7) ) ,7) ) ,-7) +transpose(((transpose((transpose((X|X) ,4) |X) ,4) +transpose((((transpose((X|X) ,-7) +transpose((transpose(X,4) |arpeggio(X) ) ,12) ) +transpose(((transpose(arpeggio(X) ,-5) +transpose((X+transpose(X,-7) ) ,4) ) +transpose(transpose(X,4) ,7) ) ,4) ) +transpose(transpose((X+transpose(X,12) ) ,-7) ,7) ) ,-7) ) +transpose((step(transpose(transpose(X,-5) ,-5) ,12) |transpose(((X|X) |transpose(X,4) ) ,-5) ) ,7) ) ,4) ) +transpose(((arpeggio(step(X,12) ) +transpose(transpose(X,-5) ,-7) ) |(transpose(transpose(transpose(transpose(X,-5) ,4) ,4) ,-5) |(echo(echo(X,4,6) ,4,6) +transpose(((step(X,12) +transpose((X+X) ,12) ) +X) ,12) ) ) ) ,7) ) ,4) ) +(arpeggio((shuffle((transpose((echo(transpose(X,-7) ,4,6) +transpose((X|X) ,12) ) ,-5) +transpose(transpose(transpose(transpose((X+transpose((X+transpose(X,7) ) ,7) ) ,-5) ,-5) ,-5) ,7) ) ) +transpose((transpose(transpose((transpose(transpose(((transpose(X,-5) +transpose(echo(X,4,6) ,4) ) +transpose(transpose(transpose(X,4) ,4) ,7) ) ,4) ,4) +transpose((((X+transpose(transpose(X,-7) ,7) ) |(((X+X) |X) |transpose(transpose(X,-5) ,-7) ) ) |(X+(X|X) ) ) ,7) ) ,-7) ,-7) +transpose((((arpeggio(arpeggio(transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-7) ) ) +transpose(transpose(transpose((X|X) ,-7) ,4) ,4) ) +transpose(arpeggio((((transpose((X+transpose(X,12) ) ,4) +(transpose(X,-5) +transpose(X,7) ) ) +transpose(((X|X) +((X+transpose(X,4) ) +transpose(X,7) ) ) ,4) ) +transpose(shuffle(X) ,7) ) ) ,7) ) |step(((step(X,12) +transpose(((X|X) +transpose((X|X) ,7) ) ,12) ) +transpose(transpose(transpose((X+((X+transpose(X,4) ) +transpose(X,7) ) ) ,4) ,-7) ,12) ) ,12) ) ,12) ) ,12) ) ) +transpose(shuffle(shuffle((((transpose(((((X+transpose(X,4) ) +transpose(X,7) ) +transpose((X+transpose(X,12) ) ,4) ) +transpose((X|(X|X) ) ,7) ) ,-7) +transpose(step(((X|transpose(X,4) ) +shuffle(transpose(X,-5) ) ) ,12) ,12) ) +transpose(echo((arpeggio(step(X,12) ) +(transpose((shuffle(X) +transpose(X,12) ) ,4) +((X+transpose(X,7) ) +transpose((transpose(X,-7) |step(X,12) ) ,12) ) ) ) ,4,6) ,7) ) +transpose(((((((X+transpose(X,12) ) +transpose(arpeggio(transpose(X,4) ) ,7) ) |((((X+transpose(X,4) ) +transpose(X,7) ) +transpose(step(transpose(X,4) ,12) ,12) ) +transpose(transpose((shuffle(X) +transpose(transpose(X,-5) ,7) ) ,-7) ,12) ) ) +transpose((transpose(X,4) |((arpeggio(X) +transpose(X,7) ) +transpose((((X+transpose(X,12) ) +shuffle(X) ) +(((X|X) +transpose(X,4) ) +transpose(transpose(X,-5) ,7) ) ) ,7) ) ) ,4) ) +transpose(((transpose(transpose(X,-7) ,4) +transpose(transpose(X,4) ,4) ) +transpose(X,7) ) ,7) ) +transpose((shuffle(((transpose(X,-7) +transpose(((X+X) +(X+transpose(X,7) ) ) ,4) ) +transpose(transpose(shuffle(X) ,4) ,7) ) ) +(transpose(transpose(transpose(X,-7) ,-5) ,4) +transpose(((transpose(X,-7) |echo(X,4,6) ) +transpose(X,7) ) ,12) ) ) ,12) ) ,7) ) ) ) ,7) ) ) ) ) +((step((transpose(arpeggio((((step(transpose((X+transpose(X,7) ) ,-7) ,12) +transpose(step(((((X+transpose(X,4) ) +transpose(X,7) ) +transpose((X+X) ,7) ) +echo(X,4,6) ) ,12) ,7) ) +step(transpose(((((X|X) |X) +transpose((transpose(X,-7) |X) ,4) ) +transpose(transpose(X,4) ,7) ) ,-7) ,12) ) |transpose(transpose(transpose(arpeggio(X) ,-7) ,-5) ,-7) ) ) ,4) +transpose(shuffle(echo((((((transpose(X,4) +transpose((X|X) ,7) ) +transpose(transpose((X|X) ,-7) ,4) ) +transpose(transpose(X,-7) ,7) ) +transpose((transpose(X,-5) +transpose(echo(X,4,6) ,12) ) ,4) ) +transpose((((X|X) +transpose(X,12) ) +transpose(transpose(X,-5) ,12) ) ,7) ) ,4,6) ) ,-7) ) ,12) +transpose(transpose(((((transpose(transpose(transpose((shuffle(transpose(X,-5) ) |(X+transpose((X+transpose(X,12) ) ,12) ) ) ,-7) ,-7) ,4) +transpose((step(transpose((X+transpose(X,12) ) ,-7) ,12) +(transpose(arpeggio(X) ,-7) |echo((X|X) ,4,6) ) ) ,12) ) +((((((X+transpose(X,4) ) +transpose(X,7) ) +transpose(transpose((X+X) ,-5) ,7) ) |(X+transpose(transpose(X,4) ,7) ) ) +transpose(echo(shuffle(transpose(X,-7) ) ,4,6) ,7) ) +((transpose(((echo(X,4,6) |(X+transpose(shuffle(X) ,12) ) ) +transpose((transpose(X,-5) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,12) ) ,7) ) ,-5) +transpose((transpose((shuffle(X) +transpose(X,4) ) ,4) +arpeggio(transpose(X,-5) ) ) ,12) ) |(transpose((transpose((X+transpose(X,7) ) ,-5) |(X|transpose(X,-5) ) ) ,4) +transpose(echo(transpose(X,-5) ,4,6) ,7) ) ) ) ) +transpose(shuffle(transpose(arpeggio((((echo(((X|X) +(X+X) ) ,4,6) +transpose((echo(transpose((X+transpose(X,12) ) ,4) ,4,6) +transpose(transpose(X,-5) ,7) ) ,4) ) +transpose((transpose(X,-7) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,7) ) ,7) ) +transpose((step(X,12) +transpose((X|X) ,12) ) ,12) ) ) ,-7) ) ,7) ) +transpose(transpose(transpose(transpose(((transpose((transpose((X+transpose(X,-7) ) ,-7) +transpose((((X+X) +transpose((transpose(X,-7) |(transpose(X,4) |step(X,12) ) ) ,4) ) +transpose(echo((X+transpose(X,12) ) ,4,6) ,7) ) ,4) ) ,-7) +transpose((transpose(step(((((step(transpose(X,4) ,12) |(X|X) ) +transpose(((X|transpose(X,-5) ) +transpose(((X+transpose(X,7) ) |(X+transpose(X,7) ) ) ,12) ) ,12) ) +transpose(transpose(X,4) ,4) ) +transpose(transpose(arpeggio((X+transpose(X,7) ) ) ,-5) ,7) ) ,12) ,-5) +transpose(transpose(echo(transpose((echo(X,4,6) +transpose(((transpose(arpeggio(X) ,4) +transpose(arpeggio(transpose(X,4) ) ,4) ) +transpose((X+X) ,7) ) ,12) ) ,-5) ,4,6) ,4) ,7) ) ,4) ) +transpose((transpose(X,4) +transpose(step((echo(X,4,6) +X) ,12) ,7) ) ,7) ) ,-5) ,-5) ,-7) ,7) ) ,4) ,4) ) +transpose((((((transpose(arpeggio((X+(X+X) ) ) ,-5) |(((X+X) +transpose((echo(X,4,6) +transpose(((X|X) +transpose(X,7) ) ,7) ) ,12) ) +transpose((X+transpose(transpose(X,-5) ,7) ) ,-5) ) ) +transpose(transpose(arpeggio((transpose((transpose(X,-5) +(X|X) ) ,-5) +transpose(transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-7) ,12) ) ) ,4) ,12) ) +((((X+(X+transpose(transpose((X|X) ,-5) ,7) ) ) |(transpose(X,-5) +step(X,12) ) ) +(transpose(((arpeggio(X) +(X+transpose(X,7) ) ) |((X+transpose(X,12) ) |echo(arpeggio(X) ,4,6) ) ) ,4) |((transpose(X,-7) +(X+transpose(transpose(X,-5) ,12) ) ) |((transpose(X,4) |(X+transpose(X,7) ) ) +(step(X,12) +transpose(transpose(X,4) ,12) ) ) ) ) ) +transpose(echo(((transpose(X,-5) |(((X+transpose(X,12) ) +transpose((X+transpose(X,7) ) ,4) ) +transpose(arpeggio(X) ,7) ) ) |shuffle(echo(transpose((X+transpose(X,12) ) ,-5) ,4,6) ) ) ,4,6) ,7) ) ) +transpose(step(((transpose((X+transpose(step(X,12) ,12) ) ,-7) +transpose(transpose(transpose(step(X,12) ,-5) ,-5) ,7) ) |X) ,12) ,7) ) +transpose(((((shuffle(transpose((((((X+transpose(echo(X,4,6) ,7) ) +arpeggio(transpose((X|X) ,4) ) ) +transpose(transpose(((X+transpose((X+transpose((X|X) ,12) ) ,4) ) +transpose((X+X) ,7) ) ,-5) ,4) ) +transpose((((shuffle(X) +transpose((shuffle(X) +transpose((X+X) ,7) ) ,7) ) +transpose(((transpose((X|X) ,-5) +transpose(transpose(X,4) ,7) ) +transpose(echo(((X+transpose(X,7) ) |X) ,4,6) ,12) ) ,4) ) +transpose(transpose(transpose(X,-5) ,4) ,7) ) ,7) ) |transpose((transpose(transpose(transpose(X,-5) ,4) ,-7) +shuffle(transpose(X,-5) ) ) ,4) ) ,4) ) +transpose(transpose((((transpose(transpose(X,-7) ,-5) +shuffle(transpose(X,-7) ) ) |transpose((transpose((X|X) ,4) +(transpose(X,4) +transpose(X,12) ) ) ,-5) ) +(transpose(arpeggio(step(((X|X) |transpose(X,-7) ) ,12) ) ,4) |(transpose(transpose(X,-5) ,-5) +transpose(step(X,12) ,7) ) ) ) ,-7) ,7) ) |shuffle((transpose(((transpose(((echo(X,4,6) +transpose((X+transpose(X,12) ) ,4) ) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,7) ) ,4) +transpose(transpose((shuffle(transpose(shuffle((X+transpose(X,7) ) ) ,-7) ) +shuffle(transpose((X|X) ,-7) ) ) ,-7) ,4) ) +transpose(transpose(X,4) ,7) ) ,-7) |echo(transpose(((step((X+transpose(X,12) ) ,12) +transpose(transpose(transpose(step(X,12) ,4) ,-5) ,4) ) +transpose(transpose((echo(X,4,6) |transpose(arpeggio(X) ,-7) ) ,-5) ,7) ) ,-5) ,4,6) ) ) ) +transpose(((transpose(transpose(arpeggio(((X+transpose((transpose((X+transpose(X,7) ) ,-5) +transpose((X+transpose(X,12) ) ,7) ) ,7) ) +echo(transpose(transpose(echo(X,4,6) ,4) ,4) ,4,6) ) ) ,-5) ,-7) +transpose((echo((transpose(((X|transpose(X,-5) ) +transpose(transpose(X,4) ,12) ) ,-7) |(X+transpose(transpose(X,-5) ,4) ) ) ,4,6) +transpose((echo((transpose(X,4) +(X|X) ) ,4,6) +transpose(transpose(transpose((((transpose(X,4) +transpose(transpose(X,-5) ,4) ) +transpose(transpose(X,-5) ,7) ) +transpose((X+X) ,12) ) ,-5) ,-7) ,7) ) ,12) ) ,7) ) +arpeggio(transpose(arpeggio((X|transpose(X,4) ) ) ,4) ) ) ,7) ) +step(((transpose(transpose(((step(transpose(((((X+transpose(X,7) ) +transpose(X,4) ) +transpose(X,7) ) +transpose(shuffle(X) ,7) ) ,4) ,12) +transpose((((step(X,12) +transpose((X+transpose(X,-7) ) ,12) ) +transpose((arpeggio(X) |(X+X) ) ,4) ) +transpose(transpose((step(X,12) +echo(X,4,6) ) ,-5) ,7) ) ,4) ) +transpose(transpose(((X+X) +transpose((X+transpose(X,7) ) ,7) ) ,-7) ,7) ) ,-5) ,4) +transpose((arpeggio(transpose((step(shuffle(X) ,12) +transpose(arpeggio(X) ,7) ) ,-7) ) +transpose((transpose(X,-5) +transpose(transpose(X,4) ,12) ) ,-7) ) ,4) ) +transpose((transpose(echo((transpose(transpose(((((X+transpose(X,4) ) +transpose(X,7) ) +transpose(transpose(X,4) ,4) ) +transpose((X+transpose(X,12) ) ,7) ) ,-5) ,-5) +transpose(shuffle(transpose((X+transpose(X,12) ) ,4) ) ,7) ) ,4,6) ,4) +transpose(step(transpose(transpose(step(((transpose(X,-5) +transpose((X|X) ,4) ) +transpose(step(X,12) ,7) ) ,12) ,4) ,-5) ,12) ,7) ) ,7) ) ,12) ) ,12) ) ,7) ) ) ,-7)
random seed used was 229115035

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