1. "The wind sang" personifies the wind, giving it human-like qualities. The verb "sang" suggests a melodious or mournful sound, rather than a harsh or destructive one.
2. "Her mournful song" further emphasises the emotional quality of the wind's sound. The adjective "mournful" implies a sense of sadness or sorrow.
3. "Falling leaves" paints a vivid picture of autumn leaves dropping from the trees. The use of the present participle "falling" creates a sense of movement and change.
4. The combination of these elements creates an image of the wind as a mournful singer, lamenting the passing of autumn and the approach of winter. The phrase captures the beauty and melancholy of the season, and the way in which nature's cycles evoke human emotions.