Yes in deep meditations there is an energy that is built up and if our body is not adequately trained to handle the energy some things can go wrong. But I guess when meditation is done regularly on a step by step basis, it is pretty safe.
I love the sound of mantras and chantings etc for it really energizes us.
The mind is a powerful tool and with adequate concentration it creates whatever we want to see. We see the God that we believe in too exactly the way we expect our God to be.