Every mantra begins with the word ॐ (Aum/Om). (Ex. Aum Namho Bhagwate Vasudevaya Namah etc.)
ॐ itself is considered a mantra in Ayurveda.
My Questions:
Om denotes the supreme Brahma:
omiti brahma omitīdaṃsarvam [Tait. Up. - 1.8.1]
Om is Brahman. Om is everything here.girām asmy ekam akṣaram [BG - 10.25]
Of sound vibrations I am the single syllable (OM)
But as we know God is threefold in nature, the same is the case for the single syllable Om. It consists of three different letters A, U, M which are the seed of all other letters, sounds, and words.
sa vā eṣa omityetadātmābhavat sa tredhātmānaṃ vyākuruta omiti tisro mātrā etābhiḥ [Mait. Up. 6.3] Meaning
He(God) came to have Om as his soul. He divided into three parts. So Om is the three units (a,u,m).
Now the letters A, U, M can be signified differently as Brahma, Vishnu, Siva, or creation, preservation, annihilation, or satva(goodness), rajas(passion), tamas(ignorance). The Mandukya Upanishad which deals only the pranava (Om) defines the three units as below:
jāgaritasthāno vaiśvānaro'kāraḥ prathamā mātrā [Mandu. Up. - 9]
Waking state is the first unit (A)svapnasthānastaijasa ukāro dvitīyā mātrā [Mandu. Up. - 10]
Dream state is the second unit (U)suṣuptasthānaḥ prājño makārastṛtīyā mātrā [Mandu. Up. - 11]
Sleeping state is the third unit (M)
These three states are related to a person. But these are also synonymous to creation, preservation, annihilation and other meanings when analyzed from the universal point of view.
Om is the primeval sound from which everything originated. By Om speech is held together:
yathā śaṅkunā sarvāṇi parṇāni saṃtṛṇṇānyevamoṃkāreṇa sarvā vāksaṃtṛṇṇoṃkāra [Chg. Up. 2.23.3]
Meaning
Like with a spike(stem or branch of a tree) all leaves are hold together, through the syllable Om all speech or voice is hold together.
So it is said that, without the presence of Om at the beginning all the following letters of the mantra will fall apart and hence won't work. Om at the beginning holds the rest of the mantra together. So on a similar context the Manu Smriti also says:
Let the Brahmin always pronounce the syllable Om at the beginning and at the end of (a lesson in) the Veda; (for) unless the syllable Om precedes, (the lesson) will slip away (from him) and unless it follows, it will get scattered. [Manu - 2.74]
Om is the seed mantra from which every other letter and mantra originated. Hence, om goes at the beginning of the Veda mantras while reciting it. Because chanting of the Vedas begins from Om, it is also known as udgitha (chanting of Veda mantra).
omityetadakṣaramudgīthamupāsīta [Chg. Up. - 1.1.1]
One should worship Om as the udgitha
I think this answers all the four questions you asked.
The word aum consists of three sounds: a (as 'u' in 'hut'), u (as 'o' in 'loot') and m (as 'm' in 'ham'). These three sounds are considered to constitute all the words spoken by people i.e., all the words consist any one or combination of these three sounds.
In another sense, the word is considered to represent the Trimurtis. The sound a symbolises the creation of the universe, thereby denotes Lord Brahma. The sound u symbolises the existence of the universe, thereby denotes Lord Vishnu. The sound m symbolises the end or the destruction of the universe, thereby denotes Lord Shiva.
There is a separate Upanishad called Maandookyopanishad which speaks about the greatness of aum alone. It says that:
aum is the primeval word which stands for the entire universe permeated by Brahman and therefore Brahman itself.
That is why it is recited at the beginning and end of every mantra. Since it denotes the ultimate Brahman itself, it is considered to be the superior mantra. Moreover, this article reports that the tonoscope image of the word aum matches with the Sri Yantra.
When we chant AUM, it produces a vibration in us which resonates with the universal vibration of AUM, and we are elevated from our everyday minds to relationship with our true Self. We chant AUM to be in tune with the true Self. The sound AUM, when chanted, vibrates at the frequency of 432 Hz, which is the same vibrational frequency found throughout everything in nature.
In addition the vibrations and rhythmic pronunciation also have a physical affect on the body by slowing down the nervous system and calming the mind similar to meditation. When the mind is relaxed, your blood pressure decreases and ultimately the health of your heart improves.
The answer is an excerpt from krishnamurthys and experiencehinduism
When I was young, I used to see the OM symbol in Hindu temples. I used to wonder at its meaning. It is only later that I learnt that OM is clearly explained in Mandukya Upanishad (MU). MU is one of the ancient classical Upanishads commented upon by Acharya Shankara. It comprises of only 12 shlokas (verses). It is also one of the most fascinating for reasons that will become clear as we go through the short text. I found, however, that the significance of OM was not clear to me even after going through MU. I fully understood only after reading Vivekananda on OM. I will first of all go through the text of MU and then discuss the significance of OM as explained by Vivekananda.
OM DEFINED in MU
MU opens with a startling claim:
This letter that is OM is all this. All that is past, present, or future is verily OM. And whatever is beyond the three periods is also verily OM.
Mandukya Upanishad 1
One question arises in the mind of a reader when faced with such a claim. How can a mere word be all this, past, present, future and even beyond these periods? Before we can have any answer to this question, let us see what else does MU say.
BRAHMAN AND SELF IN MU
All this is surely Brahman. This Self is Brahman. The Self, such as It is, is possessed of four quarters.
The first quarter is Vaisvanara whose sphere of action is the waking state, whose consciousness relates to things external, who is possessed of seven limbs and nineteen mouths, and who enjoys gross things.
Taijasa is the second quarter, whose sphere of activity is the dream state, whose consciousness is internal, who is possessed of seven limbs and nineteen mouths, and who enjoys subtle objects.
That state is deep sleep where the sleeper does not desire any enjoyable thing and does not see any dream. The third quarter is Prajna who has deep sleep as his sphere, in whom everything becomes undifferentiated, who is a mass of mere consciousness, who abounds in bliss, who is surely an enjoyer of bliss, and who is the doorway to the experience (of the dream and waking states).
This one is the Lord of all; this one is Omniscient; this one is the inner Director of all; this one is the Source of all; this one is verily the place of origin and dissolution of all beings.
They consider the Fourth to be that which is not conscious of the internal world, nor conscious of the external world, nor conscious of both the worlds, nor a mass of consciousness, nor conscious, nor unconscious; which is unseen, beyond empirical dealings, beyond the grasp of the organs of action, uninferable, unthinkable, indescribable; whose valid proof consists in the single belief in the Self; in which all phenomena cease; and which is unchanging, auspicious and non-dual; That is the Self, and That is to be known.
Mandukya Upanishad 2-7
In these 6 shlokas, MU describes the various states of the Self or Brahman. These various states are the waking, dreaming, deep sleep state and what it says is the uninferable, unthinkable, fourth state. MU uses significant terms to describe these states. For example, it calls the dream state as Taijasa which means radiant. Why does it call the Self in its dream state as Taijasa? I asked this question to a Swami of the Ramakrishna Order. He told me that the dream state of the Self shines like the Sun.
RELATION BETWEEN OM AND SELF
That very Self, considered from the standpoint of the syllable denoting It is OM. Considered from the standpoint of letters constituting OM, the quarters of the Self are the letters of OM, and the letters are the quarters. The letters are a, u. and m.
Vaisvanara, having the waking state as his sphere, is the first letter a, because of the similarity of pervasive or being the first. Who knows thus, does verily attain all desirable things, and becomes the foremost.
He who is Taijasa with the state of dream as his sphere of activity is the second letter u of OM; because of the similarity of excellence and intermediateness. He who knows thus increases the current of knowledge and becomes equal to all. None is born in his line who is not a knower of Brahman.
Prajna with his sphere of activity in the sleep state is m, the third letter of OM, because of measuring or because of absorption. Anyone who knows thus measures all this, and he becomes the place of absorption.
The partless OM is Turiya - beyond all conventional dealings, the limit of the negation of the phenomenal world, the auspicious, and the non-dual. OM is thus the Self to be sure. He who knows thus enters the Self through his self.
Mandukya Upanishad 8-12
MU now connects the dots and shows how the various states of the Self are described by OM. MU does not answer, however, why OM was chosen by the Rishis to describe all.
Vivekananda on OM
We still do not have the answers to the question raised previously. How can a mere word be all this? I looked next at what Vivekananda has written on OM in the hope of getting an answer. Vivekananda has written the following in his free translation and commentary of Patanjali's Yoga Sutra 1.27:
The commentator says the manifesting word of God is Om. Why does he emphasize this word? There are hundreds of words for God. One thought is connected with a thousand words; the idea "God" is connected with hundreds of words, and each one stands as a symbol for God. Very good. But there must be a generalization among all these words, some substratum, some common ground of all these symbols, and that which is the common symbol will be the best, and will really represent them all.
In making a sound we use the larynx and the palate as a sounding board. Is there any material sound of which all other sounds must be manifestations, one which is the natural sound? Om (Aum) is such a sound, the basis of all sounds.
The first letter, A, is the root sound, the key, pronounced without touching any part of the tongue or palate; M represents the last sound in the series, being produced by the closed lips, and the U rolls from the very root to the end of the sounding board of the mouth. Thus, Om represents the whole phenomena of sound-producing. As such, it must be the natural symbol, the matrix of all the various sounds. It denotes the whole range and possibility of all the words that can be made.
Apart from these speculations, we see that around this word Om are centered all the different religious ideas in India; all the various religious ideas of the Vedas have gathered themselves round this word Om. What has that to do with America and England, or any other country? Simply this, that the word has been retained at every stage of religious growth in India, and it has been manipulated to mean all the various ideas about God. Monists, dualists, mono-dualists, separatists, and even atheists took up this Om. Om has become the one symbol for the religious aspiration of the vast majority of human beings.
Take, for instance, the English word God. It covers only a limited function, and if you go beyond it, you have to add adjectives, to make it Personal, or Impersonal, or Absolute God. So with the words for God in every other language; their signification is very small. This word Om, however, has around it all the various significances. As such it should be accepted by everyone.
The Complete Works of Swami Vivekananda, Volume 1, Patanjali Yoga Sutra, Commentary I.27
It is after reading Vivekananda that the significance of OM became clear to me. Om signifies the totality of all possible sounds. Om stands for the infinite possibility. So it was chosen by the Rishis to signify the Self and its waking states.
Sri Ramakrishna on OM
This still leaves one other question. Since there were several Rishis, how did all Rishis agree to that single word? I found the answer in the Gospel of Sri Ramakrishna:
Sri Ramakrishna:"You explain 'AUM" with reference to 'a', 'u', and 'm' only."
Mahima:"'A', 'U', and 'M' mean creation, preservation and destruction".
Sri Ramakrishna:"But I give the illustration of a gong - 'tom', t -- o--m. It is the merging of the Lila in the Nitya: the gross, the subtle and the casual merge in the Great Cause; waking, dream and deep sleep merge in Turiya. The striking of the gong is like the falling of a heavy weight into a big ocean. Waves begin to rise; the Relative rises from the Absolute; the Causal, Subtle, and gross bodies rise from the Great Cause; from Turiya emerge the states of deep sleep, dream and waking. From the Absolute to the Relative, and from the Relative to the Absolute. Therefore I give the illustration of the gong's sound 'tom'. I have clearly perceived all these things. It has been revealed to me that there exists an Ocean of Consciousness without limit. From it come all things of the relative plane and in It they merge again. Millions of Brahmanda rise in that Chidakasa and merge in It again. All this has been revealed to me."
(The Gospel of Sri Ramakrishna, Chapter 33, With Various Devotees)
This is the answer! All Rishis agreed about the word OM since the same word was revealed to them as it was revealed to Sri Ramakrishna.
Patanjali Yoga Sutra has a discussion on Om.
The Sacred Word designating Him is Pranava or the Mystic Syllable OM.
Patanjali Yoga Sutra I.27
Repeat It and Contemplate Upon Its Meaning.
Patanjali Yoga Sutra I.28
From that comes realization of the Individual Self and the obstacles are resolved.
Patanjali Yoga Sutra I.29
Repetition (japa) of OM as part of a mantra obtained from a Guru purifies the mind, removes the obstacles and leads to the direct experience of God.
Om is a mantra, or vibration, that is traditionally chanted during any Hindu Ritual. Originated from the Hindu scriptures, the mantra is considered to have high spiritual and creative power but despite this, it is a mantra that can be recited by anyone. It’s both a sound and a symbol rich in meaning and depth and when pronounced correctly it is actually AUM.
HOW IS IT CHANTED?
The mantra OM or AUM consist of 4 syllables: A, U, M, and the silent syllable.
The first syllable is A, pronounced as a “awe” which is sustained for a short time period. The sound originates from the back of your throat and is stretched out. You will start feeling your solar plexus and chest vibrating.
The next syllable is U, pronounced as a prolonged “oo,” with the vibration and the sound will gradually move along your upper palate and you will slowly start to feel your throat vibrate.
The third syllable is M, pronounced as a prolonged “mmmm”. While pronouncing this syllable, your teeth must be gently touching each other. As you enunciate, the top of your throat will begin to vibrate.
The final syllable is the deep silence of the Infinite. As intelligence rises from the deep silence, you have to merge your chant from the ‘M’ to the deep silence.
The three syllables of of AUM is said to embody the divine energy which is more commonly known as Shakti, and the 3 main characteristics are creation, preservation and liberation.
WHY DO WE CHANT IT?
Everything in the universe is said to be pulsating and vibrating. Nothing in the universe is a constant. When the mantra Om is chanted, the frequency at which it vibrates is 432 Hz. Incidentally, it is the same vibrational frequency of everything present in the universe.
AUM is considered to be the sound of the universe, and it is believed that by chanting the mantra, we are physically and spiritually in sync with the various elements of nature and the universe.
One can reap positive benefits by chanting the mantra. While chanting the OM, the body’s nervous system slows down and creates a calming effect on the mind which is also caused by meditation. By doing so, the condition of the heart improves as a direct result of a relaxed mind and decreasing blood pressure.
Finally it is also a way to delineate the time of our practice from the rest of our day and signify that this is a special time in which to care for ourselves and practice being mindful.
Source: http://www.ishtadevata.com/blog/understanding-mantra-om.html#sthash.uJpzRO1d.dpuf
Om is made of 3 sounds(A+U+M). It is the sound of Purush(the unmanifest God identified as Brahman by Vedanatis) which manifests in 3 forms, creator Brahma represented by A, maintainer Vishnu defined by sound U, and destroyer Shiva identified with M. the dot on top of it represent the unmanifest, or the true state while all three states are temporary or illusion.
All those who recite Om, they actually connect with the unmanifest, the supreme father of all Gods and creation. So, first respect is paid to him either knowingly or without knowledge through all mantras.
It is the sound of Universe. It is called Pranavaakaara and has no origin. The sound can be reproduced by any form of instrument in the world.
OM? full confusion