Om

The  sound  symbol  AUM or  OM is  considered  as the  name  of this  nirguna  Brahman.
Nirguna  Brahma  upasana is  more  in  the  form  of  understanding  and  contemplation
rather  than  chanting  of  a  mantra.  Though  OM chanting  may  be  taken  up by  an
individual  who  takes  to  this  upasana but that  is  secondary  only.  The  upasana is  for
appreciating  the  underlying  Truth  which  is  the  basis  of  all  states  of  experience  and
which  is  not  opposed  to  any  experience.  The  truth  or  consciousness  or  Brahman or
Atman is  unopposed to anything; it lends its support and  basis  for everything. This is
considered as the highest accomplishment by Veda’s. Even sagunopasana is to lead one
to  this  only but  not  all  do  have  the capacity  of  mind  to  do  this  and  hence  different
upasanas are  prescribed  to  suit  different  people.  Mantra  is  obviously  a  part  of  any
upasana.
Bhagavan  Ramana  Maharshi of  Thiruvannamalai in  his  work  Upadesa Saram says:
kaya vak mana kâryam uttamam, pûjanam japa chintanam kramât. The meaning is: all
mental worship is superior to vocal prayer and vocal prayer is superior to worship with
body (hands etc. with a lot of external items), similarly contemplation is superior to japa
or  mantra chanting  and  japa is superior  to  physical  worship.  Here  japa again  is
categorized as japa of a mantra or japa of a stotra or verse (like thousand names of the
Lord Vishnu, Vishnu Sahasra Nâma or Lalita Sahasra Nâma etc.) or japa of a text (like
Srimad  Bhagavat  Purana  or Ramayana etc).  Thus  japa has  a  role  leading  to
contemplation  of  the  Brahman,  which  is  neither  nirguna nor  saguna.  Nir-guna or
attributeless is the word used in comparison to sa-guna or with-attributes. But in itself
the Self  or Brahman or Atman can be called as  saguna or  nirguna because it alone is
advaitam, non-dual. It is  free  from sajatiya, vijatiya or swagata bhedâs. Bhedâs means
differences. The Truth is  free  from differences born out of itself or due to members of
the same class or from the members of other classes because it alone is. It is partless like
space but is not space because waking space is negated by the dream space. Thus what
is there is only One Non-Dual Brahman, which is non-separate from the Self, and thus
the  scripture  reveals  that the  Self  or  Atman is  the  Whole,  pure consciousness.  This
contemplation is aided by superimposing the waking, dream and deep sleep on AUM or
OM sound symbol.
AUM or OM consists of three sounds. The  first one is A pronounced as A in All. The
second sound is U pronounced as OO in Room . The third sound is M pronounced as m
in  Rim or  Dim.  The  first  sound  is  a  guttural  sound  and  it  is  the  first  sound  that  is
produced when one opens the mouth and it is the first letter in Sanskrit. The third or last
sound is the sound which is produced when one closes the mouth and it is not possible
to produce any other sound after producing this  sound and at the most one can extend
this to mmmmmm… This sounds like a  humming bee. The  second  sound is produced
by  twisting  the  lips  and  the  tongue.  This  is  the  sound  of  rounding  off  all  sounds  in
between the first and the last sounds that can be produced by the human acoustics. Thus
AUM or OM covers all sounds. In the world every object is associated with a name and
it is not possible to separate the object and the name of the object. All names are nothing
but  sounds.  Thus  AUM represents  all  the  objects  of  the  world.  The  first  sound  A
represents  the  entire  waking  world.  The  second  sound  U  represents  the  entire  dream
world and the sound M represents the deep sleep state. The silence, which  follows the last  closing  sound,  represents  the  Truth  that  supports  all  these  three  states.  This  is
considered as the  fourth  state, as though. This  silence can be  first looked upon as the
silence between two AUMs but in reality AUM is raising in this silence and is sustained
by this silence and is going  back into silence. Thus silence  remains as the  basis of all
AUMs. One  fails to  recognize this silence when there is the sound of AUM so even it
becomes difficult to recognize the Nirguna Brahma as the basis of all Saguna. It is like
a  wave  is  rising  in the  ocean  and  is  sustained by the  ocean  and  is  resolving  into the
ocean. There is no wave without an ocean. Ocean becomes the cause of the wave. But in
reality both wave and ocean are nothing but water. There is no wave or ocean without
water. From the standpoint of water there is only water. Water is not even the cause of
waves. Waves and  ocean are  nothing  but water. Thus whatever is  here is  nothing  but
Brahman, which is of the nature of Existence Knowledge Bliss Absolute.