Yoga is more than meditation and breathing exercises. It also requires cultivating an awareness of one’s own psychology – the traits that one has inherited from one’s parents, culture and environment. One must patiently trace the source of every impulse which arises before it is acted upon. (i.e. “Am I doing this for glory, out of fear, out of habit, etc”). This introspection constitutes the practice of Jnana Yoga (Yoga of knowledge and discrimination), which must be undertaken in order to cleanse the soul of its lower egoistic formations.
When the Yoga enters into deeper states of trance, the heat of the Kundalini begins to course through the body, the subtle body is activated and the brain experiences a reverberating natural silence. The Yogin experiences a sense of purity, rejuvenation and alertness within. At this point, one may hear subtle sounds in the ear, smell burning incense or floral fragrances (which have non-worldly origin) and gain sight into the occult worlds. The sounds which the Yogin hears tend to vary depending on the inner plane of consciousness to which one is currently attuned. This post is a collection of these subtle sounds as noted in various ancient scriptures. As we see, there is lot of similarity in these descriptions.
One of the techniques Sri Aurobindo and the Mother recommended for meditation was contemplating on Akasha or Space. This has been discussed in the section on Widening of consciousness. The source of this technique lies in the Yoga Upanishads. Out of the 108 Upanishads, there are 21 which are known as the Yoga Upanishads. These contain various methods of Dharana (i.e. one-pointed concentration). This post contains a brief overview of these techniques as given in the book Dharana Darshan by Swami Niranjanananda Saraswati of the Bihar School of Yoga.