The idea of a “contrail,” a trail left behind after something’s passing, is interpreted in several ways in this piece. The electronics serve as a “contrail” to the flute, capturing and sustaining certain resonant frequencies of the flute’s sound. The whole work is also a contrail of Bach’s aria, “Aus Liebe will mein Heiland sterben” from St. Matthew’s Passion, about the compassion of Christ’s self-sacrifice. Most of the material in this piece was derived from a spectral analysis of the aria. The compositional process involved using an original computer algorithm running in ACToolbox to “morph” smoothly between spectrally generated material and the original flute melody found in the aria. This interpolation occurs in nearly every parameter of the music (rhythm, pitch, dynamics, etc.). The effect is that one musical idea gradually recedes from the texture revealing a second idea hidden within or beneath it. As this patina dissolves, notes or phrases from the original aria are sometimes heard to emerge from the resonant, fluttering abyss from which the work begins.

A stereo version of Contrails exists as well.