As saguna Mantras have form, nirguna Mantras are without form. There are no deities or personalized aspects of God to be invoked. Rather, one uses the abstract Mantras and Vedantic formulas to assert identification with all the creation. Because people are of many different temperaments, not all spiritual aspirants are drawn to a personal deity. Many perceive the universe as diverse energy patterns, all connected and interrelated, and stemming from one Source or Primal Cause.
For this type of temperament, the abstract mantra creates a vibration in which the meditator identifies with the whole of the Cosmos. With the repetition of one of these Mantras, the meditator loses his individual identity and merges with nature. He avows that he is identical with that homogeneous substratum, that energy or power of existence, which underlies and permeates all that exists.
All Mantras are hidden in OM, which is the abstract, highest Mantra of the cosmos. OM is the manifest symbol of the Sabdabrahaman vibration, or God; but it must not be equated with the Divine. The universe has come from OM, rests in OM and dissolves in it. AUM, as it is sometimes written, covers the threefold experience of man; A represents the physical plane, U represents the mental and astral plane, and M represents the deep sleep state and everything beyond reach of the intellect. The transcendental sound of OM is heard only by Yogis, not by the ordinary ear.
Letters of the alphabet are emanations from OM, which is the root of all sounds and letters. A is the first sound the vocal apparatus can utter, and M is the last. In between is the middle range of U. The three sounds comprising OM encompass all sound. There is no language , music or poetry outside its range. Not only does all language and thought arise from this word, but also the energy vibrations of the universe itself.
Because of its universality, OM can be used as a Mantra by all who are unable to find a guru. However, its very universality and lack of particular form make it very difficult for a beginner to grasp. The mind must be very strong to be able to concentrate on formless and abstract Mantras such as OM.
Japa meditation on OM has a tremendous influence on the mind. Vibrations set up by this word are extremely powerful. By holding the hands over the ears and intoning it, one can experience its vibrations on a rudimentary physical level. No other sound similarly intoned will have the same vibrational power within the head.
Correctly pronounced, the sound proceeds from the navel with a deep and harmonious vibration, and gradually manifests itself at the upper part of the nostrils. The larynx and palate are the sounding boards; no part of the tongue or palate is touched. As the U is pronounced, the sound rolls from the root of the tongue to the end of the sounding board of the mouth. M is the last sound, and is produced by closing the lips. Pronounced merely as spelled OM will have a certain effect upon the nervous system, and will benefit the psyche. Pronounced correctly, it arouses and transforms every atom in the physical body, setting up new vibrations and awakening dormant physical and mental powers.
Just as the various deities are aspects of One Supreme, so the various bija, or seed Mantras are aspects of the supreme Mantra, OM. Bija Mantras are seed letters directly derived from the fifty primeval sounds, and are very powerful. Generally a bija Mantra consists of a single letter, although some, such as HREEM, are compounded. Each has a significant inner mystic meaning , although on the surface the sound itself appears to have no meaning at all. Each element of the universe has its corresponding bija. The sounds for ether, air, fire, water and earth are, respectively, HAM, YAM, RAM, VAM and LAM. Every deity also has its own deed syllable. Because of their innate force, bija Mantras generally are not given for initiation. Japa on them may be practiced by those who are in a pure state, and their use is preceded by intricate rituals.
"Soham"(I am That I am)
The meditator is existence itself. He is without form, without quality, without past, present or future. No bonds or limitations restrict the aspirant who has Soham firmly fixed in his hand.
"Aham Brahma Asmi"(I am Brahman)
Aham Brahma Asmi is a great Vedantic formula. The meditator asserts himself to be One with the ever- present Brahman. In doing so, he denies confinement to the body and mind, and affirms unity with the Absolute.
"Tat Twam Asi"(That Thou Art)
"That" is the eternal Brahman, and "thou" is the meditator. Tat Twam Asi, is one of the greatest of the Vedantic statements, identifies the individual as one and the same with Brahaman, the Absolute Substratum of Creation.
There is no translation of OM. It consists of three letters: A, U and M. It signifies the three periods of time, the three states of consciousness and all of existence. A is the waking state, U is the dreaming state, and M is the deep sleep state. OM contains nada and bindu. Nada is the prolonged vowel sound and bindu is the humming sound, made with closed lips, with which the Mantra ends.