This first link is to the love duet from Madame Butterfly.  Just by coincidence, I have this recording somewhere.  One thing to notice is that Tebaldi is nearly always in the resonance.  Carlo Bergonzi, who plays Pinkerton is almost never in the resonance.  By this, I mean the placement of air and tone such that the resonating bones of the head and the face are engaged.  Bergonzi is straining and pushing a lot, and he is not placing the air high enough.  Consequently, he is using muscle to make the sound rather than than the head structures.  Most of the duet is too much for him.

BUTTERFLY
Vogliatemi bene, un bene piccolino,
un bene da bambino
quale a me si conviene.
Noi siamo gente avvezza
alle piccole cose,
umili e silenziose,
ad una tenerezza
sfiorante e pur profonda
come il ciel, come l’onda del mare.

PINKERTON
Dammi ch’io baci
le tue mani care,
mia Butterfly!
Come t’han ben nomata
tenue farfalla…

BUTTERFLY
Dicon ch’oltre mare
se cade in man dell’uom
ogni farfalla d’uno spillo
è trafitta
ed in tavola infitta!

PINKERTON
Un po’ di vero c’è:
e tu lo sai perché?
Perché non fugga più.
Io t’ho ghermita…
Ti serro palpitante.
Sei mia.

BUTTERFLY
Sì, per la vita.

PINKERTON
Vieni, vieni…
Via dall’anima in pena
angoscia paurosa.
È notte serena! Guarda:
dorme ogni cosa!
Sei mia! Ah! vien!

BUTTERFLY
Ah! dolce notte! quante stelle!
Non le vidi mai sì belle!
Trema, brilla ogni favilla
col baglior d’una pupilla.
Oh! quanti occhi fisi, attenti,
d’ogni parte a riguardar!
pei firmamenti, via pei lidi,
via pel mare…ride il ciel!
Ah! dolce notte!
Tutto estatico d’amor,
ride il ciel!

BUTTERFLY
Love me with a little love,
a child-like love,
the kind that suits me.
We are a people used to
small, things
modest, quiet things,
to a tenderness gently caressing,
yet vast as the sky
and as the waves of the sea.

PINKERTON
Give me your dear hands
and let me kiss them!
My Butterfly!
How aptly you were named,
fragile butterfly!

BUTTERFLY
They say that overseas
if it should fall into the hands of man
a butterfly is stuck through
with a pin
and fixed to a board!

PINKERTON
There’s some truth in that;
and do you know why?
So that it shouldn’t fly away again.
I’ve caught you…
Quivering, I press you to me.
You’re mine.

BUTTERFLY
Yes, for life.

PINKERTON
Come along, come…
Cast all sad fears
out of your heart!
The night is clear! See,
all things sleep!
You are mine! Oh, come!

BUTTERFLY
Oh, lovely night! What a lot of stars!
Never have I seen them so beautiful!
Every spark twinkles and shines
with the brilliance of an eye.
Oh! What a lot of eyes fixed and staring,
looking at us from all sides!
In the sky, along the shore,
out to sea…the sky is smiling!
Oh, lovely night!
In a ecstasy of love
the sky is smiling!

La Mamma Morta

In La mamma morta, from Andrea Chénier by Umberto Giordano,

The story of this opera is convoluted, even for a verismo opera.  Suffice it to say that Maddalena de Coigny, an aristocrat at the time of the Terror, is pleading for her love for André Chénier, a poet used as a ploy by a character called Gérard.  You may be familiar with this aria from the movie “Philadelphia” as sung by Maria Callas.  Here Tebaldi shows herself to be a great performer while live at the Met.  The singing is highly expressive, and the sound is emanating from the resonating cavities in her head.  The placement of the air and the tone are beautiful.

La mamma morta m’hanno
alla porta della stanza mia
Moriva e mi salvava!
poi a notte alta
io con Bersi errava,
quando ad un tratto
un livido bagliore guizza
e rischiara innanzi a’ passi miei
la cupa via!
Guardo!
Bruciava il loco di mia culla!
Così fui sola!
E intorno il nulla!
Fame e miseria!
Il bisogno, il periglio!
Caddi malata,
e Bersi, buona e pura,
di sua bellezza ha fatto un mercato,
un contratto per me!
Porto sventura a chi bene mi vuole!
Fu in quel dolore
che a me venne l’amor!
Voce piena d’armonia e dice
Vivi ancora! Io son la vita!
Ne’ miei occhi è il tuo cielo!
Tu non sei sola!
Le lacrime tue io le raccolgo!
Io sto sul tuo cammino e ti sorreggo!
Sorridi e spera! Io son l’amore!
Tutto intorno è sangue e fango?
Io son divino! Io son l’oblio!
Io sono il dio che sovra il mondo
scendo da l’empireo, fa della terra
un ciel! Ah!
Io son l’amore, io son l’amor, l’amor

They killed my mother
at the door of my room
She died and saved me.
Later, in the dead of night,
I wandered with Bersi,
when suddenly
a bright glow flickers
and lights were ahead of me
the dark street!
I looked –
My childhood home was on fire!
I was alone!
surrounded by nothingness!
Hunger and misery
deprivation, danger!
I fell ill,
and Bersi, so good and pure
made a market, a deal, of her beauty
for me –
I bring misfortune to all who care for me!
It was then, in my grief,
that love came to me.
A voice full of harmony says,
“Keep on living, I am life itself!
Your heaven is in my eyes!
You are not alone.
I collect all your tears
I walk with you and support you!
Smile and hope! I am Love!
Are you surrounded by blood and mire?
I am Divine! I am oblivion!
I am the God who saves the World
I descend from Heaven and make this Earth
A heaven! Ah!
I am love, love, love.”