This Magic Moment (one in a series)
Jacques Offenbach, Barcarolle from The Tales of Hoffmann, m. 42
"Belle nuit, ô nuit d'amour," the duet that begins the Venice act of Hoffmann, is a piece that starts out enchantingly lovely and then switches midstream to an almost terrifying level of beauty. Everyone who's heard it knows that. But listening to Kiri Te Kanawa and Frederica von Stade sing it in Berkeley the other night, I was struck — not for the first time — by the fact that you can spot the exact moment where the switch occurs.
It comes at the end of the first measure that the two women sing together. Nicklausse has the melody first, alone, and then Giulietta joins in in unison. So far, so good. But at the end of that bar they peel off into parallel thirds, and as the vocal texture splits in two there are suddenly about 600 more colors in the house.
The trick is all the more stunning for being so simple. The enchantment of women's voices in parallel thirds is well attested (cf., for instance, "Mira, o Norma"). But the delayed onset here gives the whole thing an almost pedagogical feel, as though Offenbach wanted to draw your attention to it through a before-and-after juxtaposition. "This is a melody," he says. "But this is a melody...in thirds!"