Thanks - that matches my little observations and clears up a few questions I had. I did notice that spectrogram views are almost the same regardless of perceived gender except that the strongest bands and their distributions change, and also that perceived pitch isn't as dynamic as actual frequency shifts of harmonics, but didn't realize that the center frequency moving up had to do with both physical and figurative size. It makes sense.

One thing I've been feeling itchy regarding this domain is that a lot of existing resources are shallow and there aren't many gamified options even though things like rhythm game feels like a perfect fit. I think not a negligible number of people, especially young and inexperienced, are struggling with aggressive or dis-satisfied sounding voices against their intent. Just a laptop app to feedback the error between their intended voice and recognized voices to let them minimize the error feel like a useful thing to me.