I have tried to sing the tune Twinkle"Twinkle, Twinkle Little starStar" in the key of E. It seems to be the easiest key for me. The highest note is C#4.
Something seems to happen on D4. It is like I start loosinglosing chest voice and moving into head voice. But I won't call it the passaggio note that some of you guys refer to. That note seems to be on E4.
So before the primo passaggio there is another passaggio?