Frost imagines a time before humans, when the wind blew wildly and loudly wherever it happened to catch, with no real aim. A man arrives and tells it what is wrong: it is not meant to blow so hard; its true purpose is song. He takes a little of that wind into his mouth, holds it long enough to change its direction, and then blows it out “by measure”—carefully shaped, like a singer shaping breath. The result is both word and note, the sound the wind had always been reaching for.
The tone is light and fable-like, even a little playful. The speaker seems pleased by the idea that raw force can become something lovely through breath, patience, and restraint. The final lines leave a mood of quiet satisfaction, as if nature and human craft have briefly understood each other.