Step 1: Understanding hue of light.
Hue refers to the quality of colour determined by the wavelength of light. Step 2: Corresponding property in sound.
Pitch is determined by the frequency of a sound wave and plays a role analogous to wavelength in light. Step 3: Eliminating other options.
Loudness corresponds to brightness, timbre to texture, and purity to spectral composition, not hue. Step 4: Conclusion.
Therefore, pitch is the sound property analogous to the hue of light.