So by meditating on the second syllable, one lives and enjoys the world that he visualises, with his imagination. For the moon (luna) is associated with imagination, visualisation, creativity of thought, which when it goes beyond one’s control becomes lunacy, derived from luna for moon, you know that.
Maybe it is better to be more lunatic, than be a perfect saintly person who does acts of such terrible consequences. Anyway, that is a different story; we won’t discuss that now. So, he becomes an expert by meditating on the Aaa Uuu, Au sound; and being able to work on the creative aspect of his mind and having experienced the greatness there, he returns again to this earth, to further evolve to greater levels of understanding.
But, if he meditates on the highest person, with the three syllables, the three elements of Aum, Aaa Uuu and Mmm, he becomes one with the light, which is the Sun. Just as a snake is freed from its skin, even so is he freed from his sins. He is led by the chanting of the Sama hymns to the world of Brahman.
He sees the person that dwells in the body, who is higher than the highest life. The three elements, each lead to death by themselves, if separately practiced. If they are united to each other, without being separated and employed in actions well performed–external, internal and intermediate–the knower does not waver. He moves forward.
The Aum is the essence of the Rig, the Yajus and the Saman.
Continuing further, Sage Pippalada says: “With the Rig verses, one attains this world; with the Yajus formulas, one attains the inter space; and with the Saman, the chants, one attains to that which the Seers recognise, the Rishis recognise. The the wise one attains, by the mere support of sound Aum, That which is tranquil, undecaying, immortal, fearless and supreme.”
So what have we understood so far?
With the Rig, the verses, upon understanding these verses, understanding the teachings of the Rig, he attains this world. And, with Yajus, upon understanding the formulas, one attains higher levels of understanding, attains the inner space, ascending above earthly existence. With the Saman, the sacred chants tuned to lift one up to the highest state of consciousness, a state that the great Rishis recognise, he attains That. When does this happen? When he practices all the three together- the Rig, the Yajus and the Saman.
Now, says the Upanishad, the wise one attains the supreme state merely by the sound of Aum–he doesn’t have to go through the Rig, the Yajus and the Saman.
The Aum is the essence of the Rig, the Yajus and the Saman; and when the wise one takes refuge in the sound of AUM, then he attains That, which is by itself, tranquil, undecaying, immortal, fearless, and the Supreme, beyond all the three states.
Now, that state is called the Turiya, the pure consciousness. And, it underlies all other states and transcends them.