A cappella cover the beautiful and sad Turret opera from the game Portal 2 by Valve performed by Liz Baseman, Rachel Dolkas, Matt Forman, Cody Shough.

Italian Lyrics
Cara bel, cara mia bella!
Mia bambina, oh ciel (Chell)!
Ché la stima!
Ché la stima!
O cara mia, addio!

La mia bambina cara…
perché non passi lontana?
Sì, lontana da Scienza!
Cara, cara mia bambina…
Ah, mia bella!
Ah, mia cara!
Ah, mia cara!
Ah, mia bambina!
Oh cara, cara mia…

English translation
My beautiful dear, my darling beauty!
My baby, oh heavens (Chell)!
That admire her!
That admire her!
Oh my dear, farewell!

My dear child…
Why don’t you walk away?
So far, away from Science!
My dear, dear baby…
Ah, my beauty!
Ah, my dear!
Ah, my dear!
Ah, my little girl!
Oh my dearest one!

source: A Cappella Records, lyrics & translation via Half-life Wikia