(Click to enlarge video grab of a dog joining in kirtan, Golden Gate Park, 1967—see link below)
"This chanting of Hare Krishna, Hare Krishna, Krishna Krishna, Hare Hare/ Hare Rama, Hare Rama, Rama Rama, Hare Hare is directly enacted from the spiritual platform, surpassing all lower states of consciousness — namely sensual, mental and intellectual. There is no need of understanding the language of the mantra, nor is there any need of mental speculation nor any intellectual adjustment for chanting this maha-mantra. It springs automatically from the spiritual platform, and as such, anyone can take part in this transcendental sound vibration, without any previous qualification, and dance in ecstasy.
We have seen it practically. Even a child can take part in the chanting, or even a dog can take part in it. The chanting should be heard, however, from the lips of a pure devotee of the Lord, so that immediate effect can be achieved. As far as possible, chanting from the lips of nondevotees should be avoided, as much as milk touched by the lips of a serpent causes poisonous effect."
(Srila Prabhupada's Hare Krishna Address, Happening Album, 1966)
Click here to see video of a dog joining Prabhupada's kirtan at the 4:18 minute mark)