Singing can be rough, especially when you are all worn out. That is when proper technique can save you. Many of my students over the years have come to me wanting to get a more uniform sound throughout their entire range. Some of the women thought they were just altos with a limited range and could never sing any high notes because it hurt too much to try. Or, others complained that they seemed to have two different and distinct voices, one high and one low with no voice at all in the middle. Some men absolutely refused to sing high notes, preferring to grovel in the basement. They never realized that they could use different "gears" to get into their head voice or even their falcetto. They simply did not know how to navigate through the PASSAGGIO.
PASSAGGIO an Italian word meaning passage. For singers, this passage is a breaking point between two different registers in the vocal apparatus. A simple illustration of what happens is that like in a car motor, the muscles in the larynx need to shift and use different muscles to get to a higher or lower placement. They need to "shift gears" to rev up to higher rpms. Okay, that is a very simple analogy, but it works.
A singer may use his chest register rather comfortably in his lower range, but feels tight and restricted if he tries to use that placement, or that set of muscles to try to sing higher. That is his BREAK or PASSAGGIO. Some singers may have figured out a lighter higher placement (using different muscles) to sing in their high range. The sound may be beautiful and well centered, but as they descend, they lose all control because they have not learned to "shift gears" to allow different muscles to act to sing the notes in that middle register, or bridge the gap between their high and low voice qualities. They might even yodel between the two registers in a very uncomfortably embarrassing way. These singers may, in fact, have two completely different sounds in their head voice and chest register with no control at all in the mid-range.
A good voice teacher will work tirelessly to help the student work through navigating the PASSAGIO until the entire range is unified. And then, when the singing gets tough, or when the body is tired, the singer can fall back on good technique to see him through. When singers abuse their voices and do not navigate well the PASSAGGIO bad things can happen. The worst is developing vocal nodes or scar tissue build-up on the vocal folds. You don't want that! So, if you suspect that you may be experiencing problems NAVIGATING the PASSAGGIO and are at your BREAK-ing point, RUN, not not walk, to a good vocal teacher. They will see you through!