The longer the thought is kept in the mind, the stronger it becomes. The mystic keeps one thought in the mind for ten minutes, for twenty minutes. He practices this. He practices it with music. First he impresses one Raga upon his mind until it is fixed in his mind like a picture. Then he improves upon the Raga and looks at that picture like a painter who paints and then looks at his picture. Then he practices the sound only, without melody, one sound or - to break the monotony - two sounds, or three sounds. After that he hums. He keeps all feeling away. There is no anger, no bitterness, no prejudice, no attachment, nothing that keeps him bound to the ego. Then there is no outward sound; he keeps the sound in his mind. Then he begins to hear the sound of the breath, the fine sound that the ears cannot hear.