What is the upper register of the human voice when singing?

The Bee Gees ❤

Nanna, And before them, Frankie Valli of The Four Seasons. Oh, and Lou Christie.

Russell Thompson of The Stylistics is my favorite.

Dell Shannon sang in this voice regularly

Player Say what!?, I loved Lou Christie! I still listen to "Rhapsody in the Rain" and "Lightning Strikes," although it took me years to find them both.

Chico Marx- My last pupil had a falsetto teeth

Fredrico, Castrati were young boys with beautiful voices who were often "volunteered" by their parents to be castrated. Castration prevents puberty so the voice doesn't lower. They sang soprano and alto, not falsetto.

Paul McCartney in My Love (does it good).

I think Eddie Kendricks of the soul group Temptations had a unique voice.