80: ..."the chief agency by which Nature's wheel is moved in a phenomenal direction is sound.  Sound is the first aspect of the manifested pentagon since it is a property of ether called Akas and as I already said Vedic recitation is the highest Yagnam containing in itself all minor Yagnams and tending to preserve the manifested pentagon in the proper order.  In the opinion of our old philosophers sound or speech is next to thought the highest karmic agent used by man.
Of the various karmic agencies wielded by man in the way of moulding himself and surroundings, sound or speech is the most important, for, to speak is to work in ether which of course rules the lower quaternary of elements, air, fire, water and earth.  Human sound or language contains therefore all the elements required to move the different classes of Devas and those elements are of course the vowels and the consonants.  The details of the philosophy of sound in its relation to the devas who preside over the subtle world, belong to the domain of true Mantra Sastra which of course is in the hands of the knowers."—Some Thoughts on the Gita, p. 72.