When you say Om, the whole jagat, transcending language, is represented. It is neither Sanskrit, nor French, nor English, nor Hindi. This is Om, says ATMAPRAJNANANDA SARASWATI  

Om is a phonetic symbol of Brahman. All that is here is Brahman ― space, air, fire, water, earth; elementals like stars, planets, earth, mountains, ocean, river, minerals, plants, trees, animals, human beings, legs, hands, eyes, ears, kidneys, pancreas, heart and so on. These are all manifestations of Iśvara. (Iśvara means Brahman as the cause of the entire jagat). All these form Iśvara.

In phonetic sound, the A – U – M are loaded. They are word-like, but transcend all languages. “Phonetically” Om is not a Sanskrit word, nor French, nor Kannada, nor an English word. Om is a phonetic symbol of the human voice. It is only the human voice that functions uniformly. We don’t have different phonetics for different individuals.

Whether one is an Eskimo from Alaska, a puṇdit from Varanasi, a Swāmī from Rishikesh, a scholar from Harvard, a tribal from Madhya Pradesh, or a native of Andaman Islands ― ask anyone to open his or her mouth and make a sound, it will be the sound A―

Atmaprajnananda Saraswati

Indian music is, in fact, intrinsically vocal music. Instruments are purely accompaniments. Instruments cannot produce lyrics. Lyrical production is through the human voice only. There is nothing like a live human voice. It is the best musical instrument ever made. Therefore, a person is advised to do a-kāra sādhanā early morning. ‘A’ is the basic sound.

Then when you close your mouth, the sound you produce is M―. All other sounds ka, ca, ṭa, ta, pa, ya-ra-la-va, śa-ṣa-sa, ha, ña-ma-ṅa- ṇa-nam, all sounds in all dialects are between A and M. After closing the mouth, one cannot produce any other sound. Even the first letter that a child learns is ammā. Mom also is the same thing ― close your mouth, and open and close again ― Mom. M is a good word ― ammā. It is purely phonetic. Language is picked up afterwards. The child creates the language. This is how the human voice works. That means all sounds, all words, all letters are between A and M.

Now, all forms are Iśvara. Severally one gives each form, one name ― flower, petal, stamen, water, Sun. For each one of them, there is a form and name. This is a flower. The same object in Hindi is phūl ― a different word. Each language has different words for the same object. All these forms make one form; but severally viewed, myriad forms each have a name. Names can be in any language. The word will consist of letters, syllables. There are various letters in various languages and dialects. All letters are sounds; and all sounds are between A and M.

In Sanskrit, the first letter is A, and the last letter is ha. akārāt hakārāntasya ― ātma- saṃstham. In Om, the first letter is A, the last letter is M. Between A and M, are all sounds, all letters in all languages referring to the various forms in the jagat. All of them are covered by one sound. You round them up. akāra-makārayoḥ  ― tayor-madhye ―. You round up your lips and what you get is U. U is labial, A is guttural. When you combine both, you get O. They have to blend. When they blend, a single vowel O is obtained, called diphthong in English. When you say Om, the whole jagat, transcending language is represented. It is neither Sanskrit, nor French, nor English, nor Hindi. This is Om.  

Om is the meaning of So’ham

The upadeśa ― tat tvam asi means sa (tat) aham asmi ― ‘That Lord I am’. Here saù is a loaded pronoun. aham means ‘I’. It is an equation. When soh’am is understood, it is like the wave understanding that ― ‘I am water’. In this understanding, certain things are given up. The ‘wave-ness’ is to be given up; ‘ocean-ness’ is to be given up. What is satyam, is neither wave, nor ocean. In soham, sa is Almighty, All-knowing, All-powerful; aham is small-knowing, small-powerful and is of limited skills. Both saḥ and aham are mithyā, since ocean-ness and wave-ness is mithyā.

So’ham (minus) S (minus) ha = Om.

This is the rahasya of so’ham. Om is not an ordinary word.

As a sound symbol, as a phonetic word Om is an onomatopoeic word, like cooing of the cuckoo. The cawing of the crow kākā is an onomatopoeic word.

kākaḥ  kṛṣṇaḥ pikaḥ kṛṣṇaḥ, ko pikakākayoḥ bhedaḥ |

vasantakāle samprāpte, pikaḥ pikaḥ, kākaḥ kākaḥ ||

In warp and woof, woof is onomatopoeic. It is easy to remember. Warp is the long yarn that is fixed. When the spindle moves, it makes the sound ― woof, woof, so the width yarn is called woof. Similarly, they say ― He has pooh-poohed him. Suppose there is a whiff of smoke. You pooh-pooh it. In onomatopoeic words, the very sound becomes the word. Om is like an onomatopoeic word; it is purely based on human voice.

Chanting of Oṃkāra generates tyāga bhāvana

So being a word symbol ― pratīka ― it can be used for dhyānam ― contemplation and meditation. When you say everything is the Lord, it is dhyānam. When you begin to see the meaning of the words, it is nididhyāsana ― contemplation. In dhyānam, one can chant Om also. The only problem is that, it generates a particular urge to give up everything. Therefore, only Sannyāsis are asked to chant Om all the time. The whole day they chant Om, nothing but Om. By anubhava, it is observed that chanting of Om generates tyāgavṛtti ― renunciation. This has been the experience of people. There is no logic. Therefore, men always say that women should not chant Om, since the family, the community, the whole society depends on women. The gṛhasthas do not chant Om alone, they add something following Om ―  om namo nārāyaṇāya, or om namaḥ śivāya.

Om is considered to be mahābīja, the basic mantra. It is a mantra because it is a pratīka. Additionally, it is a word invoking the source of blessing. A basic mantra is called bījamantra. Generally, basic mantras are single-syllable mantras. Sometimes, there are two syllables also in some bījamantras.

There is a meditation technique called TM ―Transcendental Meditation. It is in fact a brand name created just like different Yoga forms have created brand names to sell.  Yoga has become a marketable item. TM was franchised, and marketed. For a franchise, you can become a TM initiator. In fact, of all the techniques available in the market for a price, TM is the best. They have fourteen syllables. Out of them, they specially choose one for you, and give it to you. Mostly people get aim. It is the Saraswatī bījamantra. One does not chant any bījamantra singly. The only bījamantra chanted singly is Om. Any other bījamantra is never chanted singly. One may chant ― aiṃ hrīṃ sarasvatyai namaḥ.

hrīm ― represents the Śakti of the Lord ― prosperity, health, clarity (growing knowledge), symbolised by Saraswatī; hrīm includes power to destroy also.

aim ― represents only the auspicious Śakti of the Lord, i.e. blessings of knowledge represented by Saraswatī.  śrīm ― represents Lakṣmī.

aiṃ hrīṃ sarasvatyai namaḥ means ― My salutation to Goddess Saraswatī who is the auspicious Śakti of the Lord. This is how the mantra should be chanted.

 A Ph.D. in Sanskrit, Atmaprajnananda Saraswati is the author of nine books ― Dasasanti, Rupasiddhi, Nomenclature of the Vedas, Rsikas of the Rgveda, Om: The Sound Symbol, Vision of Advaita Vedanta in Taittiriya Upanishad, SubhashitaPrajnavali, Bhagavadgita – a study, and Suktas and Stotras.