What might have been interesting, if 3-channel had become standard, would have been to dedicate the center-channel to vertical information, by raising this speaker above the L/R speakers.
Exactly what I mentioned before and started experimenting with (extensively),
and starting back in 1987-88.
Depending upon what kind of performance was recorded, one could create a sound stage that had width along a lateral axis, and height in the center. The center-microphones would be dedicated to capturing a portion of the performance that realistically would emanate from this level.
As singers, violins and wind instruments commonly are worked at head-level, this might have created a rewarding reproduction of actual verticality in sound reproduction, rather than today's imagined.
As you play with the position of the center microphones in the vertical axes,
and experiment with their recording heights that can also be help by physical structures, as helpful sound techniques, and finally by adjusting the center channel speaker's height in your listening sessions, you can create anything you want. Even Height. :b
Quality microphones with the right directivity pattern, from different designs, and imaginative technics using physical structures in helping to capture the height of the recording venue, are right there at our dispositions, already.
It is only up to us to add that third center channel speaker to our front soundtage in order to recreate the full panoply of the 3D holographic soundstage in all planes; horizontal, vertical, and laterally in depth.
And then play with its own physical height (center speaker), and choose the appropriate music recording selections, or get back at it and recreate new quality and realistic recordings from real acoustical live venues with these 'magic' (great) musical performances from the best musicians, conductors, orchestras (Classical), bands (Jazz, Blues, ...) of the World.