Not sure about the speech sounds Jean, though the article I remember reading mention 26 possible speech sounds in human beings. I think the article was published in Scientific American years ago. Maybe a Google could come up with it. I’ll check.

Regarding tones, we're all constricted by the physics of Earth. All the fractions of tones would still exist inside the box, be it half-tones, quarter-tones, etc.

The feedback will certainly keep my interest on this topic.

John smile