Dutch pianist Nora Mulder (performing in the pouring rain on this photo) will be premiering À.X. for piano solo in the Muziekenhuis in Nijmegen, on May 14. À.X. (a hommage to Yannis Xenakis) is closely related to Fern (2006) and Kranz (2005). Dating back to 2005, it was the first sketch in a series of arborescences, which was waiting for a performer to be finished in this form.

In À.X. the sonic equivalent of the Lindenmayer axiom – a fractal-like model of the growth of trees and branches – is presented unfiltered, polyphonic and relentless in the first part. À.X. is modelled after piano pieces by Yannis Xenakis – virtuoso repertoire that Mulder performs so powerfully and elegantly.

The sonic process of growing branches and diverging polyphony is repeated as a chorale in the second part (titled Phyllotaxis, the arrangement of the leaves on the stem of a plant). In Phyllotaxis, a cloud of singing cicadas inhabits the instrument; referring to (in Xenakis' words): "The collision of hail or rain with hard surfaces, or the song of cicadas in a summer field. These sonic events are made out of thousands of isolated sounds; this multitude of sounds, seen as a totality, is a new sonic event."