- does one need some form of Diksha to chant OM or can it be chanted by anyone?
- Are there any benefits of simply chanting OM?
Om is a Mantra, so chanting Om constitutes Mantra Japa. Other names for it are Pranava Mantra, TAraka Mantra etc.
Om represents the Adi Dvani (primordial sound) and is an Ekakshara Bija Mantra (mono-syllabled seed Mantra). It also represents the Brahman in the MAntrik level.
EkAkshare tathA kute traipure mantra nAyike |
Shtri datte swapna lavdhe cha sidhhAdi naiva sAdhayet ||
O MantranAyika! - For mono-syllabled Mantras, Kuta Mantras, Tripura Mantras and those which are women-given (given by StriGurus) or those which are obtained in dreams, considerations like SiddhAdi are not required.
KulArnava Tantram 15.98
The above verse says that for all mono-syllabled Mantras Siddha-Asiddha and other such considerations are not required (usually they are required for Mantras).
This verse proves that Ekakshara Mantras are Mantras.
Few examples of such Mantras (besides Om) are Hrim (Shakti Bija), Srim (Lakshmi Bija), Klim (KAma Bija), Aim (VAg Bija), Hum, Haum (Shiva Bija), Gam (Ganapaty), Dum (DurgA) etc etc.
And, Om definitely requires initiation.
EkAkshmarapradAtAram yo gurunchA vamanayet |
SwAnam yoni satam gatvA chandAlatvam vApnuyAt ||
One who insults the Guru, who is the giver of ekAkshara (or OM), gets the womb of dogs for hundred births and thereafter gets chandAla-hood (a low human birth).
KulArnava Tantram 11.74.
So, Guru is the one who gives the initiation of Om.
Also, in all scriptures, including the Tantras, there are certain restrictions regarding the initiation of Om.
SwAhA Pranava Samyuktam Sudre Mantram Dadad DvijAh |
Sudro NirayagAmi SyAd BrAhamano YAtyadhogatim ||
The Brahmin who gives a Sudra a Mantra, that has the Pranava (OM) and SwAhA in it, goes himself downwards and the Sudra too visits hell.
Devi YAmala Tantram
So, Om is a Mantra with just a single syllable and like all Mantras it will also require initiation.
It is actually the foremost of all Mantras too and it usually sits at the front of almost all Mantras.
Any Vedic recital must also start and end with the pronunciation of Om.