The transition between a singer’s lower and upper register is referred to as “passaggio” in classical singing. The lower register is referred to as the “chest voice” by some singers and voice coaches, while the upper register is referred to as the “head voice” by others. Without training, the singer’s voice may break, he or she may have difficulty holding notes, or he or she may be unable to form certain vowel sounds.
The “chest voice” refers to the lower register of a singer’s voice, where the vocal cords are short and thick, and the resonance of a singer’s voice is felt through the chest. This is a powerful range that is used in everyday conversation. The “head voice” is named after the fact that the vocal cords are thinner and stretched in this range of notes, and the sound resonates in the cheekbones and teeth. The vocal cords in each register are controlled by different muscle groups.
Each singer’s passaggio will be in a different range of notes. Male and female singers have the same difficulty singing through the transition, but at different points on the scale, depending on their gender and range. The passaggio is generally found between B-flat and F-sharp above, and it spans three to seven semitones. Some singers have two areas of transition; the lower is referred to as the primo passaggio, and the upper is referred to as the secondo passaggio.
The vocalist will notice a change in note tone and quality while singing in his or her passaggio. A sudden shift in vocal registration from head to chest, or vice versa, may occur. He or she might drop a note or have difficulty pronouncing words. Some professional singers find it difficult to sing for long periods of time in the transition zone, which limits the songs or roles they can perform.
A singer can move smoothly through the entire passaggio range with training without losing tone quality, volume, or clarity. Learning to control the throat, jaw, and breath placement are some of the techniques used. A vocalist can spot the breaks and smooth over the difficult notes by practicing gliding up and down the registers. Knowing the problem allows for more relaxed singing, which helps to avoid the muscle tension that makes bridging the passaggio difficult.
Another technique aims to improve the weaker register. The muscles that control the vocal cords in the other register are relatively undeveloped in some singers who naturally fall into their upper or lower registers. Singing exercises strengthen the muscles that aren’t used as much, making the upper and lower registers more equal in strength, allowing the vocalist to blend the upper and lower registers in the passaggio range.