A parent watches their young daughter play Beethoven on a grand piano, and the instrument seems to come alive with pleasure. The big black Steinway is described as flashing its teeth in a broad, friendly grin, as if it enjoys the child’s playing. Then the speaker hears a deep, rumbling, beautiful roar of laughter — not actual sound, but a warm, imaginative impression of the piano joining in.
The mood is tender and playful. The speaker feels proud and moved, hearing something joyful in the child’s music. Instead of a formal performance, this moment feels like a happy conversation between the girl and the piano. The poem turns a living room practice session into a small, magical scene full of affection and delight.