Thank you all for the responses!
@g2the2nd Thanks for the link. Yes, a very similar effect. It’s not "real sounding", much in the same way that many producers / sound engineers are fond of panning the drum kit all the way across the sound stage. But nonetheless interesting.
@sns I realize that the way I described it, it sounds like it was very in-your-face. But it was more subtle than that. It was a very gestalt-like thing. It was in part why it took a couple of songs to perceive it. You could listen to the concert as a whole and not notice it (and in fact none of the 9 other people I was with -- of which one other was a musician -- noticed it). But once you shifted into hearing it (much like those 1980’s-era stereogram photos where you cross your eyes to see the 3D image), then you could bask in this virtual keyboard.
@corelli Yes I like the SET / full range driver analogy. I think the sheer simplicity of this sound system, the absence of the complications of reflection, and the sound engineers’ maniacal attention to detail all combined in this uber-cool way...

