Final answer:
The story of soul music spreading cross-culturally through personal interaction and media represents an example of cultural diffusion.
Step-by-step explanation:
The story of Renata tuning the radio to soul music and an elderly Eastern European man discovering and sharing this music with his sister in Bulgaria is an example of cultural diffusion. Cultural diffusion is the process by which an idea, product, or cultural practice spreads from one culture to another. In this story, the soul music, which is part of Renata's cultural environment, travels to Bulgaria through the man's interaction, thereby integrating into the sister's cultural repertoire and broadening her musical landscape.