Poor vocal control is one of the things associated with ASDs.. In fact, what you describe is also a problem I have, though my mother has made me aware of it all my life - doesn't mean I was able to fix it.
The technical word for it is "Prosody".
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By simply doing what they are designed to do something large and magnificient happens. In this sense they show us how to live; The only barometer you have is your heart. When you spot your flower, you can't let anything get in your way. - John Laroche