"Hello there," says Isabella, looking for someplace acceptable to sit. "Did your mother tell you why I'm here?"
(She's going to declare him, at a minimum, "trainable", regardless of whether he sounds more like a frog than like an angel. But she has to hear him sing for that declaration to make sense.)
"Beautiful!" applauds Isabella. "You're a little quiet, but that's okay, so am I. I can tell you like to sing. You know that if I take you to join the choir you'll need to live in or near the Eyrie - in a room with one of the other boys or possibly in the Gabriel School. You can send letters, of course, but it would be a few months without coming back here to see your parents."
"I can take you with me today if you can get ready. You're not afraid of heights, are you?"
"Okay! Why don't you run along and pack and say your goodbyes?" Isabella says brightly. "It's a bit of a long flight, so you might want to pack a snack, too. The Eyrie is far from here."
"All set?" Isabella asks. "We can tie your bag to my belt loop so there's no risk of dropping it."
And she picks up Nathaniel, gently and carefully, and goes aloft.
"Let me know if you have any trouble breathing, or if you're cold," she says, "and I can fly lower or slower or both."
"I don't think I ever told you my name. It's Isabella," says Isabella conversationally, as they reach a reasonable cruising-with-mortal-passenger altitude.
"It's a lovely name. You know, the first leader of the host at Cedar Hills was named Nathaniel. Although he went by Nathan."
"I study history in my spare time, so I know these things," says Isabella. "What do you like to do besides sing? Practice for the choir is a few hours a day, but you'll have time to do other stuff too."
For that matter, now she's not even sure if he likes singing. But she didn't have any other ideas for legitimate ways to get him out of the house and directly under Delilah's purview, and she would really need to check with Delilah first before pulling even a small-scale equivalent of the Archangel Gabriel's Exodus of the Jansai Women at the behest of the angel Obadiah, barging in and commanding the release of the abused member of the household on pain of Jovah's thunderbolts.
"Well, you could probably locate a teacher, if you looked, but you could easily find yourself too busy to have time to work on piano," she says. Carelessly. This is not an angel who cares whether Nathaniel plays the piano, certainly not.
She can't ask this kid point-blank if his father hits him. She can't. There's no way he doesn't, but Nathaniel would assuredly lie to her.
So she'll just have to get him set up and then use the months before the Gloria to get Micaiah to talk to him, that's all. Micaiah will have a better shot if he's willing to try.
And failing that she can always just tell Delilah everything.