Aum Is All This And Also That Which Is Not All This!
It Is The Primordial Self-Resonance That Created All The Cosmoses.
It Is Also Pre-primordial through Innumerable PathWays.
Om is not a mere word.
In the beginning was the Word
and the Word was with God
and the Word was God.
According to eastern traditions OM is the Word in this Revelation. It Is the Beeja Mantram [Seed Mantram] of All Mantrams [Divine Resonances] and Mownams [ Vast Cosmic Silences ] .
Let me quote Mandukyopanishad
"Ometyedakshram idam sarvam ~ tasyopavyaakhyaanam bhootham bhavat bhavshyateti sarvam-omkaara eva ~ yachaanyat trikaalaateetham tadapy-omkaara eva".
"OM The Imperishable is All This. In Elucidations the past present future are verily "Om" Itself. If verily there Exists anything other than these three states of Time even that is OM."
Om is composed of three Sounds Aa U M. "Aa" represnts the waking state of consciousness. "U" represnts the dream state of consciousness and "M" represents the deep sleep state of Consciousness .
"Aum" [OM ]together represents the fourth state of Consciousness called Turiya Avastha when one becomes the Witness of All three states and transcends into Samaadhi[Satori].
OM is used all over in the Vedic Mantrams and Tantric Mantrams too.
It Is The Seed Of All.
Even Buddhist and Jaina scriptures and teachings accept OM unconditionally.
OM Mani Padma Hum
[ OM the jewel lotus blooms ]
OM Hrim Kleem
[ used by Taantriks in All Indian traditions. ]
Om Hari Hi Om
[ OM Hari the All pervasive Vishnu verily OM ]
Is the general Mantram used before any auspicious ritual.
Om Maha Ganapathaye nama:
Om Nama Shivaaya
Om Namo Naaraayanaaya
Om Namo Lakshmi-Narasimhaaya
etc are Mantrams used for meditation and prayer.
Om has innumerable synonyms most important being Pranava
[The Primordial Resonance/ Pre-primordial Self resonance].
There are cassettes with just OM recited perpetually resonantly~
There are also cassettes with "Om Namo Naaraayanaaya" and "Aum Nama Shivaaya"
etc. recited perpetually resonantly" .