Echosphere is a speculative Design Futures project that imagines an amusement park hundreds of years in the future powered entirely by music, soundwaves, and personalized audio data. Each ride is driven by an individualized playlist, creating a unique experience for every rider based on rhythm, tempo, and genre. The park is organized into distinct lands categorized by musical styles, with rides named after music terminology to reinforce sound as both structure and energy source. Through world-building and futures thinking, Echosphere explores how music could evolve beyond entertainment to become infrastructure, examining how deeply personal data might shape shared public experiences in far-future environments.