Then conches and kettledrums, tabors and drums and horns, suddenly blared forth, and the clamour became tremendous.

Arjuna Vishaada Yoga

Chapter 1, Verse 13

tataḥ śankhāśca bheryaśca paṇavānaka-gomukhāḥ sahasaivābhyahanyanta sa sabdas-tumulo'bhavat

Then conches and kettledrums, tabors and drums and horns, suddenly blared forth, and the clamour became tremendous.

Bhishma started roaring like a lion, blowing his conch to announce the beginning of the war. From everywhere, all the army, all the generals, all the commanders of the army, from every corner started to blow the conches, trumpets and musical instruments which belonged to the different groups of soldiers. They all made a loud sound, and this sound was so terrible that it echoed and re-echoed through the entire region and the sky. Imagine all these people blowing conches: so powerful and so strong must have been this sound, at that time, that everything around started to tremble! And not only there on the battlefield, but also in the heavens. The gods were eagerly waiting, looking down, "What is this?" All the devas were present. Even Indra was trembling in his kingdom, hoping that this war would not come up to his loka. Such was the power during that time! It didn't happen just in this physical world. It also happened in the spiritual world. Because, as I said, this great army was not made up of normal people; they were superhuman beings. They were the manifestation of devas and deities. When this sound vibrated, it vibrated throughout all creation.

When we do Kriya, what do we experience? What awakens first are the sounds. What sounds awaken when you do Kriya? You hear the thunder, you hear the ringing of the bells, you hear... What else? How many sounds do you hear before the sound of OM? Tell! Say! These are the seven sounds that resonate in the spiritual field: conches, flutes, trumpets, crickets, bells, lutes and the thunderstorm. You hear the inner sounds, the flow of the inner sounds that announce - yes! - the victory of the Self! The awakening of the Divine Consciousness! These are the sounds that one hears when one conquers all the other qualities.

The sound was clamorous and powerful! It announced the beginning of the war. They used the conch to announce the beginning and the end of war. The sound is OM. This sound which vibrates, shows that at the end, no matter how big the battle is, how strong or difficult it is, one finds one's way. At the end, everything resounds in the cosmic sound. At the end, it is through this cosmic sound that one attains Realisation. This cosmic sound is the word of God Himself. The conch and the bell are not just mere instruments. When one blows the conch, it awakens the Divinity inside. It awakens clarity inside. It vibrates and the vibration, when one blows the conch, also vibrates in your brain. The same is true of the bell. The bell is not just made for fun. You know, when we go to the church, to the temple, do we ring the bell - ting, ting, ting - and that's it? No! The bell's sound has seven vibrations. It vibrates and reacts on the seven chakras inside. The same is true of the sound of the conch. This sound is very important. Blowing the conch was not to scare others and show one's power. No! This was for themselves. It made them strong and clear. So, everybody from both sides started blowing their conches.

Bhagavad Gita