Take light, word and colour… these are three. We believe light to be different, word to be different and colour to be different. But no scientist thinks of them so. Word is sound and colour is the hue (varna). Both are waves or vibrations of light which are formed at different frequencies and are manifested in the form of light, colour or sound. Colour is light wave of frequency number 49. Sound too is a light wave of a different frequency. Colour and sound are thus not different.
Colours can be heard and sound can be seen. The instrument to hear colour is called aurotrol. By adjusting its frequencies we can begin to see sound and hear colour. These objects that seem so different from each other now become the same.
Our senses are receptive to different things. The eyes see, the ears listen, the nose smells, the tongue tastes and the skin feels touch. This is a very gross division. If we look at it from its subtler aspects then the work of the eye would be not just to see but also to listen, to smell and even to taste. The tongue cannot just taste it can listen too.