This paper presents a unified harmonic framework demonstrating that foundational equations across classical mechanics, electromagnetism, quantum theory, and cosmology emerge as harmonic overtones of a single energy decomposition principle: E = f₀ + (P × A) + ΔU. We show that established physical laws, from electrical power to quantum energy, are domain-specific projections of this universal structure. The framework derives Planck's constant as an emergent ratio (h = k/c), unifies quantum mechanics with geometric curvature, and reveals that dark matter and dark energy correspond to specific frequency regimes outside standard detection bands. This work provides deterministic testable predictions and eliminates semantic drift through proper dimensional anchoring across physical domains.