Hazel had dropped the horn enough times that she wasn't worried Ernie would be able to do any lasting damage.
"You'll want to hold it out a little bit more from your body, and only let your fingers touch the keys. Lift your palm away," she said, gesturing with her hand to where his rested lightly against the body of the instrument. It was a natural mistake to make, and Hazel could almost hear Michelle at her ear, conniving reasons to actually have to touch Ernie's arm. She giggled, but recovered in time not to let Ernie think she was laughing at him.
"That looks good. When you... go to blow into it, you don't want to blow, exactly, but make a line with your lips, parted just a little to let your breath pass through."
It was hard to explain, but showing him the way her teacher had once shown her would have been too much for Hazel. She'd have turned scarlet as a Gryffindor scarf.