The mahā-mantra is not a beautiful phrase invented five hundred years ago, and not a material sound. Picture lava rising from the very core of the earth — slowly, unstoppably, from the deepest depth. It is from exactly there, from the innermost core of Sri Chaitanya Mahaprabhu's heart, that "Hare Krishna" erupted. This Name carries the heat of His love. So don't sing it from the surface of your lips.