Hey look, it's the Met's Armonica Mama. (Will she be similarly costumed in the pit?)

And this from Armonica Mama, via the Lucia blog:

“You don’t have to be a pianist to play the armonica, but it helps. On a piano or celesta, you can play almost blindfold because you can feel where the black keys are. This is trickier. It’s just glass bowls, there’s no identifying surface, so I must always keep my eyes on them. I watch the conductor for the start, but then I can’t keep looking back and forth. I’ve been playing this since 1990, and I still have to look to find where C is!”