Abstract: Method and apparatus utilizing the method for continuous correlation of sound to light and light to sound, and more particularly a method based on a universal equation such that it can be applied to all wavelengths of light and sound seamlessly without any intuition or subjective inputs. Within this method, the entire audible sound spectrum mutually correlates to the entire visible light spectrum. A light and sound correlation apparatus disclosed is an apparatus where the wavelength of light and/or sound is input and the correlating sound and/or light is output. This invention is revealed in a plurality of embodiments for human needs, such as providing an interactive color and sound correlation display apparatus and slide rule, a color MIDI file generating apparatus, a colorized visual orchestration apparatus, an art composer apparatus, spatial information apparatus with color and sound, and a color language apparatus.