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 17 generations the expression "X" became this:
((((transpose(((transpose((transpose((step(arpeggio(((transpose(X,4) |X) +transpose(((echo(X,4,6) |X) +transpose((transpose(X,4) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,7) ) ,7) ) ,12) ) ) ,12) |transpose((X+transpose((X+transpose(X,12) ) ,7) ) ,4) ) ,-7) +transpose(transpose(shuffle(transpose(echo((echo((X+transpose(X,12) ) ,4,6) +transpose((X|transpose(X,-7) ) ,12) ) ,4,6) ,-7) ) ,-7) ,-5) ) ,-7) +transpose(((((transpose(X,4) +((X+transpose(X,12) ) +transpose(shuffle(X) ,12) ) ) +transpose(step((arpeggio(echo(X,4,6) ) +transpose(((echo(X,4,6) +transpose(X,4) ) +transpose(X,7) ) ,7) ) ,12) ,4) ) +transpose(transpose(transpose((X+X) ,-7) ,-7) ,7) ) +transpose((((((X+transpose(shuffle(X) ,4) ) +transpose(echo(X,4,6) ,7) ) +transpose((X+X) ,12) ) +transpose(step(X,12) ,4) ) +transpose((X|transpose(X,-5) ) ,12) ) ,7) ) ,4) ) +transpose((echo(echo((transpose(X,-7) +transpose(X,4) ) ,4,6) ,4,6) +shuffle(transpose((shuffle(echo(X,4,6) ) +transpose(((transpose(shuffle(X) ,-5) +transpose(transpose(step(X,12) ,-7) ,4) ) +transpose(transpose(X,-7) ,7) ) ,7) ) ,4) ) ) ,7) ) ,-5) +transpose((((((transpose((transpose((arpeggio(transpose(X,-5) ) |arpeggio((X|X) ) ) ,-7) +shuffle(transpose(X,-5) ) ) ,-5) +(shuffle((transpose(X,-5) +transpose(transpose(X,-5) ,12) ) ) +step(transpose((X+X) ,-5) ,12) ) ) |(step(transpose(X,-5) ,12) |echo(((shuffle(step(step(transpose(arpeggio(X) ,-5) ,12) ,12) ) +transpose(transpose(step((step(X,12) +transpose(((X|X) |transpose(X,4) ) ,7) ) ,12) ,-5) ,12) ) +transpose(((echo(X,4,6) +arpeggio(X) ) +transpose(((((transpose(X,4) +transpose(echo(X,4,6) ,4) ) +transpose(transpose(X,4) ,7) ) |((X|X) +transpose(X,7) ) ) +transpose(transpose(transpose(X,4) ,-7) ,7) ) ,12) ) ,12) ) ,4,6) ) ) +transpose((transpose(((arpeggio(X) +step(transpose(X,4) ,12) ) |(((X+X) +(X+shuffle(X) ) ) +((((X|X) |(X+X) ) +transpose((echo(transpose(X,-5) ,4,6) +echo(((X+transpose(X,4) ) +transpose(X,7) ) ,4,6) ) ,4) ) +transpose(arpeggio(step(X,12) ) ,7) ) ) ) ,-7) +transpose(step(transpose(echo(transpose((X+transpose(echo(X,4,6) ,12) ) ,-7) ,4,6) ,-7) ,12) ,12) ) ,4) ) +transpose((transpose(transpose(echo((transpose(X,4) +transpose(transpose(echo(X,4,6) ,-7) ,12) ) ,4,6) ,-5) ,4) +transpose(transpose(((transpose(echo((((X+transpose(X,4) ) |transpose((X+X) ,-5) ) +transpose(X,7) ) ,4,6) ,4) +transpose((transpose((((transpose((X|X) ,-7) +transpose((X+X) ,4) ) +transpose((shuffle(X) +transpose((X|X) ,12) ) ,7) ) +(echo(X,4,6) |transpose(X,-7) ) ) ,-5) +transpose((((X+transpose(X,7) ) +transpose(arpeggio((X|X) ) ,4) ) +transpose(transpose((X|X) ,-7) ,7) ) ,-7) ) ,4) ) +transpose(((step(((((arpeggio(X) +transpose(transpose(X,-7) ,4) ) +transpose((arpeggio(X) +transpose((X+X) ,12) ) ,7) ) +transpose(transpose(X,-5) ,4) ) +transpose(shuffle(((X+transpose(X,7) ) +transpose(X,12) ) ) ,7) ) ,12) +transpose((transpose(((((X+transpose(X,4) ) +transpose(X,7) ) +transpose(echo(X,4,6) ,12) ) +(transpose(X,-5) +transpose(X,7) ) ) ,4) +transpose(shuffle((step((X|X) ,12) +echo(((X+transpose(X,4) ) +transpose(X,7) ) ,4,6) ) ) ,7) ) ,4) ) +transpose(transpose((echo(transpose((X|X) ,-7) ,4,6) +(((X+transpose(X,12) ) +transpose(step(X,12) ,12) ) |X) ) ,-5) ,7) ) ,7) ) ,-7) ,12) ) ,12) ) +transpose((transpose(((transpose(transpose(X,4) ,-5) +(transpose(X,-5) +(echo(X,4,6) +transpose((X+transpose(X,12) ) ,12) ) ) ) |transpose((((shuffle(transpose(X,-7) ) +transpose((transpose(((X|X) +echo(X,4,6) ) ,-7) +(arpeggio((X+transpose(X,12) ) ) +((step(X,12) +transpose(X,4) ) +transpose(transpose(X,-5) ,7) ) ) ) ,7) ) +transpose((transpose((((step(X,12) +transpose((X|X) ,4) ) +transpose(X,7) ) +transpose(echo(X,4,6) ,7) ) ,4) +(transpose((transpose((X|X) ,-7) +(transpose(X,4) +transpose(transpose(X,4) ,7) ) ) ,4) +transpose(arpeggio(X) ,12) ) ) ,4) ) +transpose((((step((X+X) ,12) +transpose(((X+X) +transpose(X,12) ) ,4) ) +(transpose((X|X) ,-5) +transpose((X+transpose(X,7) ) ,7) ) ) |transpose((step(X,12) +(X+transpose(X,-5) ) ) ,-5) ) ,7) ) ,-7) ) ,4) +step(arpeggio(((((arpeggio(echo(X,4,6) ) +transpose(arpeggio((transpose(X,-5) +transpose(X,7) ) ) ,4) ) +transpose(((transpose(X,4) +X) +transpose(((step(X,12) +transpose(X,4) ) +transpose((X|X) ,7) ) ,12) ) ,7) ) +transpose((((transpose(transpose(X,4) ,-7) +(X+X) ) +((transpose(X,-7) +transpose(((X|X) +X) ,4) ) +transpose(((X+transpose(X,7) ) +X) ,7) ) ) +transpose((((arpeggio((X+transpose(X,12) ) ) +transpose((arpeggio(X) +transpose(X,-7) ) ,4) ) +transpose(X,7) ) +((X+transpose((X+X) ,7) ) |transpose(transpose(X,-5) ,-5) ) ) ,12) ) ,12) ) +transpose(arpeggio(arpeggio(X) ) ,12) ) ) ,12) ) ,12) ) ,12) ) |(transpose(shuffle(transpose((((((transpose(transpose((X|X) ,-5) ,-7) +transpose(X,-7) ) +transpose(transpose(X,-7) ,4) ) +transpose(((transpose(shuffle(X) ,-5) +transpose((X|X) ,12) ) |transpose((((X+X) |transpose(X,4) ) +transpose(X,4) ) ,4) ) ,7) ) |transpose(echo(transpose(((((X+transpose(X,4) ) +transpose(X,7) ) +transpose(transpose(X,4) ,4) ) +transpose(transpose(X,-5) ,7) ) ,4) ,4,6) ,-5) ) +echo(((transpose(X,-7) |(transpose(X,-5) +transpose(step((X+X) ,12) ,7) ) ) +transpose(transpose(transpose(((X+transpose((X+X) ,12) ) |transpose((echo(X,4,6) +transpose(X,7) ) ,4) ) ,-5) ,4) ,12) ) ,4,6) ) ,-7) ) ,-7) |(((step(((((((step(X,12) +(transpose(X,-5) +((echo(X,4,6) +transpose(echo(X,4,6) ,4) ) +transpose((X|X) ,7) ) ) ) +transpose(transpose(((X+X) +transpose(echo(X,4,6) ,12) ) ,-5) ,12) ) +transpose(transpose(((((shuffle(X) |echo(X,4,6) ) +transpose(arpeggio(X) ,12) ) +transpose(transpose(X,-5) ,4) ) +transpose(X,7) ) ,-5) ,7) ) |(arpeggio(transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-5) ) +((transpose(transpose(X,-5) ,-5) +transpose(transpose(X,-5) ,4) ) +transpose(transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-5) ,7) ) ) ) +transpose(transpose(shuffle(transpose(transpose(((transpose(X,4) +X) +transpose(X,4) ) ,4) ,4) ) ,-7) ,4) ) +transpose(transpose(transpose(transpose(shuffle(X) ,-5) ,4) ,-5) ,7) ) ,12) +transpose((((transpose(arpeggio(transpose((X+X) ,-7) ) ,-7) +transpose(transpose((((transpose(X,-7) +transpose(transpose(X,-5) ,7) ) +transpose(transpose(echo(X,4,6) ,4) ,4) ) +transpose((X+X) ,7) ) ,4) ,4) ) +transpose(step(arpeggio(transpose((arpeggio((X|X) ) |transpose(X,-5) ) ,4) ) ,12) ,7) ) +((transpose((transpose(X,-7) +transpose(transpose(echo(X,4,6) ,-5) ,7) ) ,4) +transpose(transpose(transpose(shuffle(transpose(X,4) ) ,-7) ,4) ,4) ) +transpose((transpose((transpose(transpose((X+transpose(X,12) ) ,-7) ,-7) |(X+(X+X) ) ) ,-5) +((X+X) +X) ) ,7) ) ) ,4) ) +transpose((transpose(((echo(((echo(X,4,6) |step(shuffle(X) ,12) ) +transpose(transpose(X,-7) ,12) ) ,4,6) |(transpose((transpose(X,-5) |transpose(X,-5) ) ,4) +transpose(step((shuffle((transpose(X,-5) +(X+transpose(X,12) ) ) ) |arpeggio(((X+transpose(X,12) ) +transpose(transpose(X,-5) ,7) ) ) ) ,12) ,7) ) ) |transpose((transpose(step(arpeggio(X) ,12) ,4) +transpose(arpeggio(transpose(X,4) ) ,7) ) ,-7) ) ,4) |(transpose((transpose(transpose((X+X) ,4) ,-5) +transpose(((transpose(transpose(((X+X) +transpose(X,7) ) ,-5) ,4) +(((X+X) +transpose(step((X+X) ,12) ,4) ) +transpose(X,7) ) ) |(arpeggio(echo(transpose((X+transpose(X,12) ) ,-7) ,4,6) ) +transpose(((transpose(X,-5) +transpose(X,4) ) +transpose(echo(X,4,6) ,7) ) ,7) ) ) ,12) ) ,-5) |transpose(transpose(X,4) ,-7) ) ) ,7) ) +shuffle(((transpose(((transpose(transpose(X,-7) ,-7) +transpose((arpeggio(arpeggio(shuffle(X) ) ) +transpose(arpeggio(X) ,4) ) ,4) ) +transpose((echo((X+transpose(X,12) ) ,4,6) +transpose(((transpose(X,-7) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,4) ) +transpose(X,7) ) ,12) ) ,7) ) ,-7) +transpose((transpose(arpeggio(step(transpose(X,-5) ,12) ) ,-7) +transpose(echo(arpeggio((X+X) ) ,4,6) ,12) ) ,4) ) +transpose(shuffle(transpose(transpose((echo(transpose((X+transpose(step(X,12) ,7) ) ,-5) ,4,6) |(echo(transpose((X+X) ,-5) ,4,6) +transpose(transpose(transpose(X,-5) ,-5) ,4) ) ) ,4) ,4) ) ,7) ) ) ) ) ) +transpose(transpose(((transpose(echo(shuffle(((((echo(X,4,6) +(transpose(X,4) +arpeggio(X) ) ) +step(arpeggio(transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-7) ) ,12) ) |transpose((transpose(X,-7) +transpose(((step(X,12) +transpose(X,4) ) +transpose(X,7) ) ,12) ) ,4) ) |arpeggio(echo((echo(transpose(X,4) ,4,6) +transpose((transpose((X+echo(X,4,6) ) ,4) |(((X+transpose(X,7) ) +transpose((X+transpose(X,7) ) ,4) ) +transpose(X,7) ) ) ,12) ) ,4,6) ) ) ) ,4,6) ,-7) +transpose(transpose((((((((transpose(transpose(transpose(X,-5) ,4) ,4) |((step(X,12) +transpose((X|X) ,7) ) +((X+X) +echo(X,4,6) ) ) ) +transpose((arpeggio(shuffle(((X+transpose(X,4) ) +transpose(X,7) ) ) ) |((shuffle(echo(X,4,6) ) +transpose((X+transpose(X,7) ) ,12) ) +transpose((transpose(X,4) +echo((X|X) ,4,6) ) ,7) ) ) ,-5) ) +transpose(transpose(echo(arpeggio(transpose(step(X,12) ,4) ) ,4,6) ,-7) ,-7) ) +transpose((step((X+transpose(X,12) ) ,12) |transpose(step((echo(transpose(step(X,12) ,4) ,4,6) +transpose((echo(X,4,6) +transpose(transpose(X,-7) ,12) ) ,12) ) ,12) ,-5) ) ,12) ) +transpose(step((transpose(transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-7) ,-7) |shuffle(transpose(((X|X) |transpose((X+X) ,-7) ) ,-5) ) ) ,12) ,4) ) +transpose(((transpose((step(X,12) +step((X+X) ,12) ) ,-7) +(transpose(X,-5) +((((X+X) +X) +transpose(((((X+transpose(X,4) ) +transpose(X,7) ) +(X+X) ) |(transpose(X,4) |X) ) ,4) ) +transpose((((X+transpose(X,4) ) +transpose(X,7) ) +transpose((transpose(X,-7) +transpose((X+transpose(X,7) ) ,12) ) ,12) ) ,7) ) ) ) +transpose(step((((X+X) +transpose(step(X,12) ,-7) ) |transpose(transpose(transpose(X,4) ,-5) ,4) ) ,12) ,7) ) ,7) ) |(((step(((transpose(X,-7) +transpose(transpose(transpose(X,4) ,-7) ,4) ) +transpose((X+transpose(X,12) ) ,7) ) ,12) +(((X+transpose(X,4) ) +transpose(transpose(X,-7) ,7) ) +transpose((X+transpose(X,7) ) ,12) ) ) +transpose(transpose((step(transpose(((transpose(transpose(X,-7) ,-5) +transpose(step(X,12) ,4) ) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,7) ) ,4) ,12) |transpose(((X|X) +X) ,-5) ) ,-7) ,-7) ) +shuffle(transpose((transpose(X,4) +transpose(transpose(transpose(arpeggio(X) ,-7) ,-5) ,7) ) ,-7) ) ) ) ,-5) ,4) ) +transpose((((transpose(((((X+X) +transpose((X|(X+transpose((X+X) ,7) ) ) ,12) ) +((shuffle(X) +transpose((X+transpose(X,7) ) ,4) ) +transpose((X+transpose(shuffle(X) ,12) ) ,7) ) ) +step(((transpose(X,-7) +arpeggio(X) ) +transpose(transpose(X,4) ,12) ) ,12) ) ,-5) +echo(transpose(transpose(transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,-5) ,4) ,-5) ,4,6) ) +transpose(((step((transpose(transpose(X,-7) ,-7) |(arpeggio((X+transpose(X,12) ) ) |(transpose((transpose(X,-5) +transpose((X|X) ,12) ) ,-5) +transpose(transpose(X,-7) ,12) ) ) ) ,12) +transpose(((shuffle(echo(X,4,6) ) +transpose(transpose(step((X+X) ,12) ,4) ,12) ) +transpose(step(step((X+X) ,12) ,12) ,12) ) ,12) ) |transpose(transpose(echo(shuffle(X) ,4,6) ,-7) ,-5) ) ,4) ) +transpose((echo((transpose(transpose((arpeggio(X) +(X+X) ) ,-5) ,-7) |(((echo(X,4,6) |X) +transpose((shuffle(step(transpose(X,-5) ,12) ) +echo(X,4,6) ) ,12) ) +transpose((transpose(X,-5) +transpose(transpose(shuffle(X) ,-5) ,12) ) ,7) ) ) ,4,6) |(transpose(arpeggio(((X+transpose(transpose(X,4) ,4) ) +echo(X,4,6) ) ) ,-5) |transpose((step((transpose(X,-5) |transpose(((X+transpose(X,7) ) +transpose(X,4) ) ,4) ) ,12) +transpose(shuffle(transpose(transpose(((X+transpose(X,12) ) |X) ,4) ,-7) ) ,7) ) ,-7) ) ) ,7) ) ,7) ) ,-5) ,4) ) +transpose(shuffle(((transpose(transpose(((((X|X) +transpose(shuffle((X|X) ) ,7) ) +transpose(transpose(((X+transpose(X,7) ) +transpose((X+transpose(step((X+transpose(X,12) ) ,12) ,12) ) ,7) ) ,-7) ,-5) ) +transpose(transpose(transpose(echo((shuffle(X) +transpose(X,4) ) ,4,6) ,4) ,-7) ,12) ) ,-7) ,-5) +transpose(((((transpose((transpose(arpeggio(X) ,-5) +transpose(((((X|X) +transpose((X|X) ,4) ) +transpose((X+X) ,7) ) +transpose(X,7) ) ,12) ) ,-5) |step((X|X) ,12) ) +(((step((X|X) ,12) |arpeggio((X+transpose(X,7) ) ) ) +transpose(echo(step((((X+transpose(X,4) ) +transpose(X,7) ) +transpose(transpose(X,-7) ,7) ) ,12) ,4,6) ,7) ) +step(arpeggio(step(step(X,12) ,12) ) ,12) ) ) +transpose(transpose(shuffle((X|X) ) ,-5) ,12) ) +transpose(transpose((((transpose(((step((X+(X+X) ) ,12) +transpose(transpose(((transpose(X,-5) |(X+transpose(X,12) ) ) +(X|X) ) ,4) ,12) ) |transpose((((X+transpose(X,4) ) +transpose(X,7) ) |(X|X) ) ,4) ) ,-5) |((transpose(((transpose(X,-7) +transpose(transpose(X,4) ,12) ) |(X+transpose(X,12) ) ) ,-7) +(transpose(transpose(transpose(X,4) ,-7) ,4) |echo(transpose(X,-7) ,4,6) ) ) +transpose((transpose(arpeggio(transpose(X,4) ) ,-5) +step((arpeggio(transpose(X,-7) ) +transpose(transpose(transpose(arpeggio(X) ,-7) ,-5) ,7) ) ,12) ) ,7) ) ) +transpose(step((((echo(X,4,6) +transpose((transpose(X,4) +echo(X,4,6) ) ,-7) ) +arpeggio(transpose((X+transpose(X,12) ) ,-5) ) ) +transpose(transpose(transpose((X+transpose(X,12) ) ,4) ,-7) ,-5) ) ,12) ,4) ) +transpose(step(((((X+transpose((X|X) ,12) ) +transpose((transpose((X|X) ,4) +transpose(transpose(shuffle(X) ,-5) ,12) ) ,4) ) +transpose((shuffle((X+(X+(X|X) ) ) ) |transpose((transpose(X,-7) +step(X,12) ) ,4) ) ,7) ) |arpeggio((X|X) ) ) ,12) ,7) ) ,-5) ,7) ) ,4) ) +transpose(((((step(transpose(transpose(shuffle((X+(X+X) ) ) ,-7) ,-7) ,12) +transpose(transpose(echo(step((arpeggio(transpose(transpose(X,-5) ,4) ) |((X+transpose(X,7) ) +transpose((X+transpose(X,7) ) ,12) ) ) ,12) ,4,6) ,-5) ,4) ) +transpose(transpose(transpose((transpose((arpeggio(((X|X) |((X+transpose(X,12) ) |transpose(X,4) ) ) ) +transpose(transpose(transpose(((transpose(X,4) +transpose(transpose(transpose(X,4) ,-5) ,12) ) +(X|(X+transpose(X,7) ) ) ) ,4) ,-5) ,7) ) ,4) +transpose(((((arpeggio(transpose(X,-7) ) |((X+X) +(X+transpose(X,7) ) ) ) |arpeggio(transpose(arpeggio(X) ,4) ) ) |(transpose(transpose(echo(X,4,6) ,4) ,-7) +arpeggio((echo(transpose(X,4) ,4,6) +transpose(shuffle((X+transpose(X,12) ) ) ,7) ) ) ) ) +transpose(transpose(transpose(X,4) ,-7) ,4) ) ,7) ) ,-5) ,-5) ,7) ) +transpose(transpose((((transpose((transpose(transpose((transpose(X,-5) +transpose((X+X) ,7) ) ,-7) ,-7) +transpose(((X|(transpose(X,-7) |(transpose(X,-5) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,7) ) ) ) +transpose(((transpose(X,-5) |transpose(arpeggio(X) ,-7) ) +transpose(arpeggio((arpeggio(X) +transpose(shuffle(X) ,12) ) ) ,12) ) ,7) ) ,12) ) ,4) +transpose(((((transpose(shuffle(X) ,4) +transpose(transpose(transpose(echo((X+transpose(X,7) ) ,4,6) ,-5) ,4) ,4) ) +transpose(((transpose(X,-5) +(echo(X,4,6) +transpose(echo(X,4,6) ,12) ) ) |transpose(((X+X) +transpose(echo(X,4,6) ,12) ) ,-5) ) ,7) ) +transpose((transpose((X+transpose(shuffle(X) ,12) ) ,-5) +transpose(X,4) ) ,12) ) +transpose(transpose(shuffle(step((X+transpose(X,12) ) ,12) ) ,4) ,7) ) ,12) ) +transpose((transpose(((((step(step(X,12) ,12) +transpose(echo(X,4,6) ,12) ) +transpose(((X+transpose(transpose(X,4) ,12) ) |((X+transpose(transpose(X,4) ,4) ) +transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,7) ) ) ,4) ) +transpose(transpose(transpose(X,-5) ,4) ,7) ) +transpose((((X+X) +step(X,12) ) +transpose(X,4) ) ,12) ) ,-5) +transpose(transpose((X+transpose(X,12) ) ,4) ,12) ) ,7) ) +(echo(echo(((echo(arpeggio(transpose(X,-7) ) ,4,6) +((X+transpose(shuffle(X) ,12) ) |arpeggio(echo(X,4,6) ) ) ) +transpose(transpose(transpose((X+transpose(X,12) ) ,4) ,-7) ,7) ) ,4,6) ,4,6) +transpose(((((X+X) +transpose(X,12) ) +transpose(step(transpose(X,4) ,12) ,12) ) +transpose((echo(transpose((X+X) ,4) ,4,6) +transpose(((echo((transpose((((X|X) +transpose(X,4) ) +transpose(X,7) ) ,-5) +transpose((((X+transpose(X,4) ) +transpose(shuffle(X) ,7) ) +transpose(echo(shuffle(X) ,4,6) ,12) ) ,7) ) ,4,6) +transpose(transpose(shuffle(transpose((X|X) ,4) ) ,4) ,4) ) +transpose((transpose((transpose(((X+transpose(X,4) ) +transpose(X,7) ) ,4) |shuffle(X) ) ,4) +(((X+transpose(X,4) ) +transpose(X,7) ) +transpose(transpose(step(X,12) ,4) ,7) ) ) ,7) ) ,12) ) ,7) ) ,7) ) ) ,-7) ,4) ) +transpose(transpose(transpose(transpose((step(transpose(arpeggio((X+transpose(X,7) ) ) ,4) ,12) |step(step(X,12) ,12) ) ,-7) ,4) ,-7) ,7) ) ,7) ) ) ,7) )
random seed used was 114689345

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