The Fantasia was commissioned by the Terezin Music Foundation in 2003. The term "virtual", borrowed from contemporary cyberspace usage, refers to the fact that the choral is not really there — that is, until the end of the piece.
It's "essence", in the form of thematic and harmonic fragments swirl around until they finally emerge into the choral itself. It makes a brief appearance, but then begins to disintegrate, vanishing into silence.
The Hawthorne String Quartet recorded the Fantasia on Naxos 8.559661.