Guru Nanak, the first Sikh Guru, was a master of sound. In Guru Nanak’s time, only a human being could be considered a Guru.
Yet, when people asked Guru Nanak who his Guru was, Guru Nanak would reply, “the Shabad.”
Guru Nanak did not look to another person to guide him. In his mastery of sound, he could meditate, penetrate into the etheric realms, and simply hear the Universal Wisdom that calls the soul home.
All teachings, all traditions, all books of wisdom are a tiny expression of that Sound of Wisdom.
Guru Nanak had such a profound level of mastery, he could perceive and hear that Universal Sound directly. He referred to it as the “shabad” or as “gurbani” – the frequency of divine guidance.
When Guru Nanak sang a song, he served as a channel for the Shabad. The songs he wrote become a living manifestation of the Shabad Guru. Then, other people could meditate upon these songs and awaken themselves.
~Resource: “The Shabad Guru,” Ideology & Beliefs, Sikh Dharma International.