Delta brainwaves are slow, loud brainwaves (low frequency and deeply penetrating, like a drum beat). They are generated in deepest meditation and dreamless sleep. Delta waves suspend external awareness and are the source of empathy. Healing and regeneration are stimulated in this state, and that is why deep restorative sleep is so essential to the healing process.
The Native American Shamans called their sacred ceremony drumming, the hoof beats of the horse the shaman rides into the spirit world, and the drum is the easiest way to access and trigger these brainwaves to enhance your internal ability to heal both yourself and others. This is a very deep trance stage which you should record the imagery soon after returning to normal waking state, because the results of the vision will be quickly forgotten and stored in the subconscious.
How will you know you have achieved this level of trance is when you are not able to hear the drum anymore and your thoughts take over the drum, when you become aware of hitting that stage, you are ready to direct your intent to healing or however you see fit to direct the energies.