How does the whole Sanskrit alphabet come from praṇava?

One example is the text Āgamarahasyam (Aṣṭamaḥ paṭalaḥ, 449 – 462), according to which praṇava is divided into five mātras: म् and two more – bindu (which is the concentration of sound vibration) and nāda (the spreading of this subtle concentration). Further, each of these mātras is split into a certain number of energy rays (kalā), each of these rays is associated with one or another Sanskrit varṇa, also this five appears in the form of pañcakāraṇeśvara, the five manifestations of Śiva (Brahmā, Viṣṇu, Rudra, Īśvara and Sadāśiva). According to the Candrajñānāgamaḥ and some other texts, five syllables of the mantraNamaḥ Śivāya’ and five kāraṇeśvaras associated with them appear from these five mātras. Let’s analyse this in detail.

The first mātra / a is connected with Brahmā, the syllable of the pañcākṣara mantra / na and the following 10 kalās and akṣaras:

कं kaṃ sṛṣṭi – the power of creation, खं khaṃ ṛddhi – the power of development, गं gaṃ smṛti – the power of memory, घं ghaṃ medhā – wisdom, ङं ṅaṃ kānti – brilliance, चं caṃ lakṣmī – success in achieving the goal, छं chaṃ dyuti – glow, जं jaṃ sthirā – stability, झं jhaṃ sthiti – existence, ञं ñaṃ siddhi – perfection.

The second mātra / u is connected with Viṣṇu, the syllable of the pañcākṣara mantra : / maḥ and the following 10 kalās and akṣaras:

टं ṭaṃ jarā – the power of longevity, ठं ṭhaṃ naṃpālinī – the power of protection, डं ḍaṃ śānti – peace, ढं ḍhaṃ aiśvari – control, णं ṇaṃ rati – pleasure, तं taṃ kāmikā – passion, थं thaṃ varadā – power to bestow boon,

दं daṃ hlādinī – happiness, धं dhaṃ prīti – attractiveness, नं naṃ dīrghā – prevalence.

The third mātra म् / m is connected with Rudra, the syllable of pañcākṣara शि / śi and the following 10 kalās and akṣaras:

पं paṃ tīkṣā – sharpness, फं phaṃ raudrī – ferociousness of expression, बं baṃ bhayā – power to instil fear, भं bhaṃ nidrā – rest in a dream, मं maṃ tandrā – state of coma, यं yaṃ kṣut – hunger, रं raṃ krodhinī – power of anger laṃ kriyā – movement, वं vaṃ utkārī – rise, शं śaṃ mṛtyu – death.

The fourth mātra is associated with bindu and with Īśvara, the syllable of pañcākṣara वा / , as well as four kalās, which are manifested in the colour of energies, and akṣaras:

षं ṣaṃ pītā – yellow, सं saṃ śvetā – white, हं haṃ kṣaṃaruṇā – red, क्षं kṣaṃ asitā – dark.

The fifth mātra is associated with nāda and Sadāśiva, the syllable of pañcākṣara / ya and the following 16 kalās and akṣaras:

अं aṃ nivṛtti – cessation of activities, आं āṃ pratiṣṭhā – establishment, इं iṃ vidyā – knowledge, ईं īṃ śānti – peace, उं uṃ indhikā – substance for sacrifice, ऊं ūṃ dīpikā – light, ऋं ṛṃ recikā – devastation, ऋृं ṛṛṃ mocikā – liberation, लृं lṛṃ parā – transcendence, लॄं lṝṃ sūkṣmā – subtlety, एं eṃ sūkṣmāmṛtā – subtle, not affected by death, ऐं aiṃ jñānāmṛtā – cognition of immortality, ओं oṃ āpyāyanī – fullness, अं aṃ vyomarūpā – emptiness, अः aḥ anantā – lack of limit (infinity).

Nātha as a manifestation of the nāda

The following definition of the term nātha is given in Gorakṣa-siddhānta-samgraha:

नाकारो नादरूपं च थाकारः स्थाप्यते सदा |

भुवनत्रयोवैकः श्रीगोरक्ष नमोऽस्तु ते ||

Reverence to Gorakṣanāth, the Nātha, who is one in the three worlds, he as a syllable “nā” – means “nāda”, and “tha” – manifested (in the three worlds).

The other part also says that nāth is one who realises the nāda or the source of own origin. In the subtle form nāda is manifested in the form of the praṇava OM, which is known as Mahāgāyatrī, and in the gross form it is known as Brahmagāyatrī; all Navanāthas, Caurashi Siddhas, Deities, Vedas, grammar (vyākaraṇa), Purāṇa, Itihāsas, etc. are manifestations of this particular Nātha-yoga.

Indeed, practices related to nāda play a fundamental role in the Nāth Tradition.