It’s a long, complex story, but here’s in short why:

Of the many names for God, OM is most likely the oldest and one of the most widely used throughout Indian history. OM’s significance as a sacred syllable in Indian spiritual culture and in yoga practice in particular can hardly be overemphasized.

In the Vedas we are told: “In the beginning was the Lord of creatures, and second to Him was the Word…the Word was truly the supreme Brahman.”

And in the Christian Bible, which uses the word OM in the form of Amen, it is stated in the fist verse of the Gospel of St. John: “In the beginning was the Word, and the Word was with God, and the Word was God.”

In other words, it is commonly understood throughout human sacred history that the idea of God and the word that symbolizes God are inseparable, that words truly are what they express.

The sacred sound OM is commonly understood in Tantra as the cosmic sound vibration that originates, maintains and reabsorbs everything in the universe. What is not so commonly recognized, however, is that the Sanskrit letter Rr, which is located in the throat, or vishuddha, chakra, is the acoustic root of the sacred OM sound.

According to Tantric science, all the 50 Sanskrit letters correspond to the 50 root sounds located in the chakras. These root sounds again represents vritties or mental tendencies (love, hate, hope, fear, etc) which are clustered around the chakras.

Hence Sanskrit is thus a language that vibrates our being from within. That’s why mantras are in Sanskrit. More profound than any other language, the sonic vibrations and combination of letters in the Sanskrit mantras harmonize our chakras and link our own individual vibration to the vibration of the cosmos.

That’s the sacred reason for the great spiritual vibes generated when chanting Sanskrit mantras during kirtan!

And that’s why this revered sound is often chanted at the beginning and conclusion of yoga practice and during so many other sacred ceremonies.

But how can the letter Rr be the acoustic root of the famous OM sound? Indeed, what is actually the origin of the OM (ওঁম) sound?

According to Tantric philosophy, the physical universe constitutes three elements: creation (A), preservation (U) and destruction (M). Hence the letters A + U = O, and the letters A+ U + M = OM. But that is not the end of the story; the dot (.) and the crescent that forms part of the OM symbol are also important.

The dot represents the unmanifest universe; the crescent represents the principle of transmutation from the unmanifest (Nirguna) to the manifest (Saguna). Hence, OM is the acoustic root of creation, preservation and destruction, plus the principle of transmutation, the devolution from pure Cosmic Consciousness to the physical world.

Even though the sonic sound OM (which symbolically includes the dot and the crescent) constitutes the acoustic root of this universe, the OM sound is nevertheless a combination of sounds, thus it requires an acoustic root of its own. In Sanskrit, the acoustic root of another root sound is called atibija, or mahabija.

So the letter Rr is the mahabija of OM. Hence, from the point of view of phonetics and the science of combining sounds (sandhi), the Rr sound is an integral part of the Sanskrit alphabet and the acoustic root of the sacred letter OM.

There is also a more down-to-earth explanation for using OM as the most sacred syllable. OM is simply the most comprehensive, most complete word to be found, simply by the way it is pronounced.

When pronouncing OM, we combine all possible positions of the throat, mouth and tongue. You start with A, the root sound, in the back of the throat without touching the tongue or palate.

You continue with the O sound by rolling through the mouth from throat to the lips. And you conclude pronouncing the sacred syllable with M by closing the lips. Hence, that is how AUM, or OM, yoga’s most sacred and complete word, is produced.

In his bestselling book, Light on Yoga, world renowned hatha yoga teacher B.K. S. Iyengar, describes the psychological and spiritual reasons for chanting OM. “The letter A symbolizes the conscious or waking state,” Iyengar writes, “the letter U the dream state, and the letter M the dreamless sleep state of the mind and spirit.” In its totality as a symbol, OM stands for the “realization of man’s divinity within himself.”

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But perhaps this simple story illustrate the reason for chanting OM better than any of the science and philosophy explained above. There was once a sadhu who owned nothing but a water pot and a book. Every day he would worship the book with offerings of flowers, and then he would read the book with intense concentration for hours on end.

One day a curious onlooker asked the sadhu what book he was reading. Without answering the sadhu simply handed him the book. When the onlooker opened it, he discovered the book contained only two words written in bold red letters on every page: Om Rama.

The sadhu explained: “What’s the use of reading many volumes of books? God is the origin of all sacred books and scriptures, and there is no difference between God and His name.”