SINGING is divine, one of the most divine activities. Only dancing is a competitor with it, it is next only to dancing. And why are singing and dancing divine activities? – because these are the activities in which you can be utterly lost. You can drown yourself in singing, so much so that the singer disappears, only the song remains, or the dancer disappears and only the dance remains. And that is the moment of metamorphosis, transfiguration, when the singer is no more and there is only the song. When your totality has become a song or a dance, that is prayer.
What song you are singing is irrelevant; it may not be a religious song, but if you can sing it totally it is sacred. And vice versa: you may be singing a religious song, hallowed by the ages, but if you are not totally in it, it is profane. The content of the song does not matter; what matters is the quality that you bring to singing, the totality, the intensity, the fire.
Don’t repeat anybody else’s song, because that is not your heart, and that is not the way you can pour your heart at the divine feet. Let your own song arise. Forget about metre and grammar. God is not too much of a grammarian, and He is not worried about what words you use. He is more concerned about your heart.