Toni has requested that I blog about the passaggio and about bocca ridente. I'll cover the former in today's post.
The passaggio (Italian for "bridge") is the area in the voice range in which a transitions from the chest voice into the head voice occurs. The exact note at which this transition happens is called the break; the passaggio includes the notes which lie a couple of semi-tones above and below the break.
The break happens at around the same pitch for all singers, male or female: the E above middle C. (The break for basses and baritones may be a semi-tone or so lower, and for some higher voices, a little higher.) This means that the break appears near the bottom of women's vocal ranges, near the top for basses and baritones, and right smack in the middle for tenors. Sorry, tenors, this makes things most challenging for you! Other singers, unless they are singing wide-ranging music like opera, can largely avoid having to negotiate much through the passaggio, but tenors (and all classical singers) must figure out how to sing here with elegance and ease.
It can be challenging to sing smoothly in the passaggio because your vocal technique must make rapid and (ideally) undetectable shifts between the two opposing registers. This requires your two registers -- chest register and falsetto/head voice -- to work together efficiently. As you come up from below your break, your chest register must gradually cede its precedence to the head voice, which takes over little by little as the notes ascend. The converse must happen as you descend in pitch. Such a delicate give-and-take can happen only when both registers are free of tension and equally strong.
The main reason that it is difficult to negotiate pitches in the passaggio is that in this tonal region, the chest voice is extremely powerful and the falsetto relatively weak. It takes skill to balance the two in a range in which their relative strengths does not match. Figuring out how to do this smoothly and easily is one of the main objectives of voice lessons. (As I see it.)
I learned from Cornelius Reid that an ascending octave exercise with the top note taken quietly helps to get the two registers operating at a similar strength level. Starting on the low pitch activates the chest voice. Going up the octave brings in the falsetto, and taking this note quietly lessons some of the power of the chest voice so that it can match the pull of the falsetto without overwhelming it.
Until your two registers are cooperating nicely in this way, you will have to resort to less desirable options for singing in the passaggio:
1) You can sing in the chest voice up to the break and then switch into falsetto for all the notes occurring above the break. The produces an unfortunate "yodeling" effect, which you may actually decide to use occasionally in comic passages.
2) You can sing everything in chest voice, pushing it higher than Nature intended, which results in shout-y high notes and an inability to sing quietly in your higher range. You hear this mostly in untrained male singers. You would have heard this from me if you attended any of my high school choral concerts.
3) You can sing everything in head voice, which makes low notes weak or unavailable and eliminates the throat-opening, stabilizing effects of the chest voice from your entire range. Since most of their notes lie above the break, many women, even accomplished opera singers, sing this way, not realizing its damaging and limiting potentials.
4) If you're a tenor without the ability to coordinate your registers, you can sing lightly in a well-developed falsetto, which has the same limitations I listed in #3. Or you can play the saxophone instead of singing.
Here's a clue to getting your registers to coordinate: they play together most nicely when you downplay their opposing qualities. For instance, the chest voice, which is by nature bright and clear, combines more easily with a bright, clear head voice (as opposed to a hootier, breathier one). I have had a lot of success getting a bright falsetto on the [a] vowel (as in "cat") to coordinate with the chest voice. Or, to go in the other direction, you could bring more head-voicey qualities into the chest voice by singing in the low range quietly on [oh] and switching up the octave above with a less overtly chesty approach which may more easily cooperate with the head voice.
A willingness to experiment is helpful. Have fun playing around with your passaggio! Go quietly at first, however, in this range; a forceful approach will never help. Let me know how your experiments are going. . . .