According to the Musician Scholars (Sangitacharya), Naad is originated from Akashstha Agni and Marut. Where the condition of soul air remains, it is called Brahmagranthi. According to the Sangeet Darpan Naad is something that is inspired by the soul, hankering (चितवस्था) that strikes the fire. Agni inspires Brahmagranthi (Prana) sole. This induces fire in the pran which begins to climb up again. Upon reaching to the navel, it is very crafty, subtle in the heart, strong in the tongue, unknowable in the head and produces the artificial sounds in the mouth. The Senses of Naad in Sangeet Damodar is considered mainly three types these are: -
1. Pranibhav (प्राणिभव),
2. Aapranibhav (अप्राणिभव) &
3. Ubhaysambhav (उभयसंभव)
The sound which is produced from the mouth is Pranibhav, the creation that comes out from harp (Veena) is called Aapranibhav, and the sound is produce from the flute is called Ubhaysambhav. Without Naad songs, vowels, melody etc. could not be possible. Also Naad has no sign or symbol; knowledge propagation can't be imagined without Naad. Therefore Naad is the Parajyoti and Brahamswarup and the whole universe is Naadatmak (नादात्मक). From the above we can say that there are two types of sounds (Naad) The Aahat and Anahata. Only the yogi can listen to Anahat Naad.
After self immolation of Sati, Lord Shiva's mind was with full of emotional panic and in state of restless mind he took Sati's lifeless body on his left soldier and started wandering like a mad. He was so much of full of vex that each and every step was creating devastation on earth. Shiva's movement in annoyance is termed as Tandav. It is a perfect blend of thrill, excitement & anger. To stop Shiva's Tandav, Vishnu threw his Chakra that dissected the body into parts. When Shiva realizes that the body is being dissected, his Tandav reached to the extremity. At zenith of his annoyance Shiva played Damru that created 14 different types of sound frequency .The sound frequency is nothing but NAAD i.e 'ECHO (Gunjaran) of nature'.
The earth i.e. Bhu-Devi could catch only 8 of those vibrations which is known as SWAR.
These swar are Sa, Re, Ga, Ma, Pa, Dha, Ni, Sa. These entire swar stands on stave line in such a fusion that they cut giving a formation of horizontal zero. As zero is placed vertically then these swar are recovered.
Naad is everywhere, it is an evidence of excellence in the heart & sole of nature, either be in nightingale or be in the cold breeze. Naad is something that embraces this whole universe.