As we chanted the Bija mantras , we were accompanied by reverberating sounds made on crystal bowls.
Each sound of the mantra corresponds to one of the seven chakras. The Chakras are said to be the energy centres of what yoga refers to as the subtle body.
Recently, in trying to explore and connect with the energy of my subtle body, I've been enjoying this 'hand to heart' exercise http://www.yogajournal.com/video/134