Om itetad aksharam idam sarvam. Om is not just a letter, but it is representing the Supreme Lord. At the beginning of our Vedic study, we start by saying, Harihi Om. This means Hari alone is Om. Hari means harati iti om – one who remains intact when everything has gone is Om. Narayana means the same – one who alone remains when everything has gone. This means Om is the foundation of everything and it is akshra– indestructible.  
 
The message of Om says we must seek the permanent only and no point in trusting on others who are themselves are impermanent.
 
The three-letter Om AUM represents:
A: ateeta: past- bhoota
U: utpanna: present: bhavya
M: meya: future: bhavat
 
That Supreme Lord – Purusha was there, is there, and will be there as changeless and complete. He is higher than Prakriti. Prakriti binds jiva -souls with sattvic (pure), rajasic (dynamic), and tamasic (dull) cords. But when the jiva – soul gets liberated, Prakriti has no longer can bind that soul. But the Supreme Lord is the goal and Lord of even the liberated souls as mentioned in the Purusha Sookta – utamritatva syeshanaha and as mentioned in the Vishnu Saharanama – muktanam parmamgarim.
 
Everyone is bound and leading a helpless life whether a prime minister or an ordinary citizen like mounted on a machine and we are bound by a cord or time and helplessly made to act. The Lord Shri Krishna beautifully says in Bhagavad Geeta
 

ishvarah sarva-bhutanam hrid-deshe arjuna tishthati 
bhramayan sarva-bhutani yantrarudhani mayaya || BG 18.61 ||

The Supreme Lord dwells in the hearts of all living beings, O Arjun. According to their karmas, he directs the wanderings of the souls, who are seated on a machine made of material energy.

 
The message of the three-letter Om makes us shed our ego to discover the joy in life.

A: means not. It is not what you know or you “a” means you do not know that.
U: means upari -up meaning The Lord is higher and beyond your comprehension
M: means meya – prameya: according to your ability try to understand.
 

Nobody can comprehend that fully. You cannot bring the whole water from the ocean but can take water from the ocean according to the size of the vessel you are carrying.
 
In a wakeful state Lord in the form of Aniruddha gives the Viswa experience and binds us with a cord of time and makes us act based on our ignorance. The foundation of our action (karya) is ignorance (karana).
 
In a dream state Lord in the form of Pradyumna gives the inner experience through a special light called Taijasa experience and binds us with a cord of time and makes us see things in our ignorance. The foundation of our unimaginable dreams (karya) is ignorance (karana).
 
Lord in the form of Sankarshana binds the soul with a cord of time and gives the total experience of ignorance in deep sleep. The foundation of our deep sleep experience is ignorance (karana). In deep sleep, there is no ego and because of this deep sleep has a blissful experience.
 
Like we do memory backup in our computers, our experiences in wakeful and dream are backed up in our deep sleep. This is called a supta prajna. We may lead a life in denial in the wakeful and dream state but the black box within cannot be erased. The medical science and police departments do sleep hypnosis to cure diseases or to extract the truth. This black box has the seeds of our karmas and is waiting for an appropriate time to manifest.
 
How to wipe out the karmas in the black box? Om says the only way is to go to the fourth state called turiya. The Supreme Lord Vasudeva who revealed to us only as Aniruddha to give outside experience, Pradyumna to give dream experience, and Sankarshana to give deep sleep experience alone can delete the seed of Karma by taking us to the fourth state called a nada.
 
The Mandukopanishad describes the turiya state as
 

amātraś caturthoavyavahāryaḥ prapañcopaśamaḥ sivo’dvaita evam auṁkāra ātmaiva saṁviśaty ātmanā’tmānaṁ ya evaṁ veda ya evaṁ veda.

 
Amatra: nada – the sound which is beyond the measure
Chaturtha: the fourth state
Avyayaharya: beyond transaction
Prapanchopashmana: No more wrong identification with the world
Shivam: purest
Advaita: Vasudeva reveals himself as Anniruddu, Pradyumna and Sankarshana and there is a difference between the form of the Lord
Atmaiva samvishat atmana atmanam: the ultimate purpose of our journey and culmination of our journey.
 
In the turiya state, one experiences the pause which is unshackled from the cord of time and becomes kalateeta.  In the wakeful, dream, and deep sleep we are bound by the cord of time and make us unsettled. Whereas in turiya state, atmaiva samvisha means one having reached the destination gets settled and does not want to move from there.
 
When the Lord Vasudeva reveals himself to give the turiya experience – one experience a flash of lighting for a very short time – not even a matra (amatra). After that experience, that person will start hearing the nada of Om continuously (amatra). Like lightning is followed by thunder, after experiencing this flash of light in the heart one hears nada continuously.
 
Music – Sangeeta is an attempt to express this inexpressible sound in various pitches – avyavaharyam. Om says if you want to be a genius in Sangeeta you must go beyond the audible sound AUM and you dive deep within to experience inner sound – antarnada. When you experience the stillness within whatever you talk is melodious to hear. In the world Parliament of religion in Chicago, many people spoke but when Swami Vivekananda uttered the words “my brothers and sisters of America” the entire audience got enraptured and stood up. 
 
The sages have given a symbol to Om as . In this symbol 3 stands for three states of our existence, wakeful, dream, and deep sleep. A curve appended to 3 symbolise turiaya – nada (amatra). A dot above that represents a bindu. A crescent represents kala. Shanta represents the cosmic egg and beyond that is atishanta – the Supreme Lord.  
 
Atishanta represents the changeless, the parament, complete and most pure – Narayana. Shanta represents Hiranyagarbha – cosmic egg– Prajapati – creator – Brahma. 
The crescent represents the destructive and liberating power of Lord Shiva. 
 
The message of Om is for all of us to seek the grace of Lord Vasudeva so that may He reveal Himself to us to give us the turiya experience.
 
One who experiences this. sees the same Lord Vasudeva everywhere. The message of Om unites us irrespective of faith and religion. Knowledge units us and ignorance divide us.