I tried to narrate a bit of information about the way singers approach the passaggio (or "change in registers). Please feel free to e-mail me at Placido 21@aol.com if you think I don't know what I'm talking about!.
Martinelli, Corelli, Carreras, Bjoerling,Gigli, Di Stefano, Baum Del Monaco 1952, Del Monaco 1961. Roswaenge, Svanholm. (The Vinay clip did not come out.)
Passaggio is a term used in classical singing to describe the pitch ranges in which vocal registration events occur. Beneath passaggio is the chest voice where any singer can produce a powerful sound, and above it lies the head voice, where a powerful and resonant sound is accessible, but usually only through training. The historic Italian school of singing describes a primo passaggio and a secondo passaggio connected through a zona di passaggio in both the male and female voice. A major goal of classical voice training in classical styles is to maintain an even timbre throughout the passaggio. Through proper training, it is possible to produce a resonant and powerful sound.