ॐ ... Aum ... Om ... is sung with the whole range of the voice from the throat to the lips. It is therefore used in India to mean THAT which is all-inclusive ... the universal and eternal Self or Ground of the universe. This is the Brahman, the Godhead from which, and in which, everything happens, in much the same way that all sounds heard on the radio and phonograph are vibrations of the diaphragm in the speaker. ॐ (Aum) represents, then, the basic vibration or energy which assumes the myriad forms and disguises of stars and planets, mountains and oceans, plants and fish, animals and men, and is also understood as the central Self, or Atman, in all beings. The sound OM is chanted, or sung silently in the head, as a focal point for deep concentration, by means of which the individual finds out that the life energy which he calls himself is One and the same as the eternal energy of the Cosmos. The Individual is thereby set free from anxiety as it recognizes the self as the infinite sea of divine consciousness manifest in all it's infinite multitude of form spread throughout the cosmos.
The Hindus do not, however, define the supreme Self, or God, as the personal governor and king of the universe. They would say, rather, that the Brahman acts or manifests the world without calculation, much as we grow our hair, circulate our blood, and form our brains and nerves. The world is not made, like an artifact, but performed, like a play -- and the one basic Actor plays all the parts.