The true source of joy is love -- love of God, love of beauty, love of wisdom, love of another human being, it does not matter which. It is all one love: a joyful awareness of dissolving boundaries of our ordinary narrow self, of being one with the reality beyond, of being made whole.
When we surround ourselves with sounds of nature, we are soothed and healed, comforted by the songs of our mother, the Earth. And who is there to sing back to the Earth?