Musica Universalis is an interactive AR art installation inspired by the ancient Greek concept of ‘Music of the Spheres.’ In this philosophy, celestial movements create music, forming a universal harmony. Using Microsoft HoloLens2, this work bring this idea to life by allowing participants to interact with planets using natural hand gestures. In their default state, the planets follow their orbits while collectively playing Debussy’s ‘Moonlight.’ However, when a participant manipulates a planet—pinching, pushing, or dragging it—the music dynamically shifts, producing echoes and altering the harmony. The closer a player brings a planet, the more pronounced the sound variations become, creating a deeply immersive experience that bridges music, space, and touch.