The ancient Mandukya Upanishad describes OM in considerable detail as the sound-body of the Universe: “OM is this imperishable Word, OM is the Universe, and this is the exposition of OM. The past, the present and the future, all that was, all that is, all that will be, is OM. Likewise all else that may exist beyond the bounds of Time, that too is OM. All this Universe is the Eternal Brahman, this Self is the Eternal, and the Self is fourfold.” (Sri Aurobindo, The Upanishads, Mandukya Upanishad 1-2, pg. 319)
Modern day scientists, attempting to capture the sounds of the universe and the planet have recorded the vibratory patterns of the planet as well as the ‘big bang” of the creation of the universe, and converted them into sounds and one can identify the vibration of OM when listening to them. OM, as the Rishis indicated, is the characteristic sound of the universal creation in its entirety.
Chanting of OM can bring about a calming and focusing influence that is palpable. Crowds of angry, fearful or upset people have been brought to a state of calm through initiation of a chant of the word OM. All contrary feelings or emotions can be brought under control through proper attention to OM.
In terms of the sadhana of the integral yoga, the use of a mantra is, like every other tool in the toolkit, something that should be applied at the right time, in the right way, under the right circumstances. It is not a tool to be used all the time, and to use it correctly, it must be done with attention to its significance and the proper intonation to create the vibratory pattern that creates the coherence of energy that is being sought.
Sri Aurobindo writes: “OM is the mantra, the expressive sound-symbol of the Brahman Consciousness in its four domains from the Turiya to the external or material plane. The function of a mantra is to create vibrations in the inner consciousness that will prepare it for the realisation of what the mantra symbolises and is supposed indeed to carry within itself. The mantra OM should therefore lead towards the opening of the consciousness to the sight and feeling of the One Consciousness in all material things, in the inner being and in the supraphysical worlds, in the causal plane above now superconscient to us and, finally, the supreme liberated transcendence above all cosmic existence. The last is usually the main preoccupation with those who use the mantra.”
“In this yoga there is no fixed mantra, no stress is laid on mantras, although sadhaks can use one if they find it helpful or so long as they find it helpful. The stress is rather on an aspiration in the consciousness and a concentration of the mind, heart, will, all the being. If a mantra is found helpful for that, one uses it. OM if rightly used (not mechanically) might very well help the opening upwards and outwards (cosmic consciousness) as well as the descent.”
Sri Aurobindo, Integral Yoga: Sri Aurobindo’s Teaching and Method of Practice, Chapter 6, Sadhana Through Love and Devotion, Mantra and Japa, pp. 165-167