The upanishad gives some very interesting views on Om in the form of a discussion between three sages. We will look at a condensed version.
“In ancient times there were three proficient in Om: Silaka the son of Salavat, Caikitayana of the Dalbhya family and Pravahana the son of Jivala. They said, ‘We are proficient in Om. If you agree, let us enter on a discussion of Om.’ ‘Let it be so’, saying this they sat down” (Chandogya Upanishad 1.8.1,2).
Ether (Akasha).
Om is a sound rising from the heart of all things; and the element of ether (akasha), which is its highest form, is consciousness, is the basis of all sound. This being so, the dialogue proceeds as follows: “What is the essence of this world?’ Akasha. All these beings arise from akasha alone and are finally dissolved into akasha; because akasha alone is greater than all these and akasha is the support at all times” (Chandogya Upanishad 1.9.1).
Remember, Om is the subject of this discussion, and since akasha is the foundation of sound, it moves on, with this: “It is this Om which is progressively higher and better. This again is endless. He who, knowing thus, meditates upon the progressively higher and better Om, obtains progressively higher and better lives and wins progressively higher and better worlds” (Chandogya Upanishad 1.9.2).
Om is the thread that runs through all levels of existence; It is the core of all worlds, emanating from the Absolute that is beyond them all. By meditating on Om we ascend higher and higher, passing through the states of consciousness that correspond to higher and higher worlds. Whatever the state of mind we are established in at the time of death, it will take us into the corresponding world. “Whatever state of being [bhavam] he remembers when he gives up the body at the end, he invariably goes to that state of being, transformed into that state of being” (Bhagavad Gita 8:6).
There is another aspect to this. In meditation, our perceptions of Om become subtler and subtler. From being a mental repetition sounding just like it would if we were speaking aloud, it becomes softer and softer, even whisperlike, eventually become a silent ideation or conceptualization while mysteriously remaining a complete word. This mutation takes place as our consciousness is moving into higher and higher states of being or bhavas. Our experiencing of this is experiencing Om and the states of awareness inherent in It.
The conclusion
The upanishad sums it up like this:
“Atidhanvan, the son of Sunaka, having taught this to Udarasandilya, said, ‘As long as among your descendants, this knowledge of Om continues, so long their life in this world will be progressively higher and better than ordinary lives. And in that other world also their state will be similar’. He who knows and meditates thus–his life in this world surely becomes progressively higher and better, and so also his state in that other world–yea, in that other world” (Chandogya Upanishad 1.9.3, 4).
Read the next article in the Upanishads for Awakening: Four Things God REALLY Wants You to Know