Why is it useful to learn to listen to the Subtle Voice?

Answers from Master Samael Aun Weor.

The student can lull himself to sleep vocalizing the letter S, like a peaceful and sweet hiss: SSSSSSSSSSSSSSSSSSSSS.

With the vocalization of the letter, he will acquire the capacity of resounding, in his brain, the SUBTLE VOICE, the SOUND OF ANAHAT, at will, which will allow him to leave consciously in the ASTRAL Body.

Samael Aun Weor. Logos, Mantra, Theurgy.