It's funny to see how someone who has "cured" his stuttering now attributes a lot of wrong explanations to the stuttering phenomenon. I think it's fairly accepted that the reason why *some* stutterers don't stutter when singing or when speaking in tandem is because different parts of your brain are activated when you do so. Broadly speaking, non-stutterers use the brains' left hemisphere to communicate, whereas stutterers use the brains' right hemisphere. I'm happy for your success :)