3D Audio

[Barry L Klein]

Could just design the widget for Surround 5.1, then have the option of
working with distinct tracts or recording that mix to a binaural head
microphone in a recording chamber.....

There was a book I read through in the bookstore awhile ago called
something like the audio technician's handbook or whatever, written in the
U.K. I think.  It had some interesting details regarding various stereo
signal phase mixing to widen the stereo sound field.  Aureal and maybe
Qsound use variations on this.  Also, I think the more harmonic content a
signal has, the better the placement in the soundfield is
perceived/achieved.  That's why a cell phone ring or high-pitched fan
oscillation is hard to pin down audibly.  Even so, it is necessary to have
cognitive clues to location or future location to achieve the 3D effect. 
But even if it doesn't always work, with the kind of music most of us are
working with, it probably still will sound cool and blow away a straight
stereo effort.
Probably a lot can be done with typical phaser circuits under voltage
control.  

Barry