What's going on here ... ?

This music was performed and recorded by Paul Henry Smith and his digital orchestra, which consists of a Mac Pro loaded with a gigantic library of orchestral sounds (millions of recordings of single notes), and two wireless Wii controllers used to control tempo and balance in real time.

This is not air conducting or merely waving arms along to a recording. In fact there is no recording per se. Mr. Smith has created a set of instructions, like a player-piano roll, that the computer follows to produce a basic performance, with the precise tempo and balance left to be determined as the music unfolds.

Crazy as it sounds, at any given moment in the music, the computer is processing thousands of instructions for pitch, instrument, style, loudness, spatial location, and shape.

This approach allows enormous expressive flexibility, not just in the tempo, but in balance and phrasing (controlled by signals from a Wii Balance Board on which the cond