Vitamin A is a group of unsaturated nutritional organic compounds, that includes retinol, retinal, retinoic acid, and several provitamin A carotenoids, and beta-carotene. Vitamin A has multiple functions: it is important for growth and development, for the maintenance of the immune system and good vision.itamin A can be found in two principal forms in foods 1  : Retinol, the form of vitamin A absorbed when eating animal food sources, is a yellow, fat-soluble substance. 2  Since the pure alcohol form is unstable, the vitamin is found in tissues in a form of retinyl ester.
pure tone is a tone with a sinusoidal waveform reciting tone such as psalm tone and recitative as in gregorian chants timbre the quality of a musical note or sound that distinguishes different types of sound production tonality a system of music based on a key center or tonic tone control a typically electronic control for affecting frequency content of an audio signal tone linguistics the pitch and pitch changes in words of certain languages tone musical instrument the audible characteristics of a musician s sound
Music tone colour or quality of sound, esp a specific type of tone colour. the quality of sound (its âcolorâ) that makes it possible to distinguish between sounds of the same pitch when made on different instruments or by different voices.