Here is the famous Christmas carol Carol of Bells melody with 4 part harmony Maha mantra (1 min video)
“The devotees of the Supreme Lord, or the persons who are in Kṛṣṇa consciousness, are called santas, and they are always in love with the Lord”- Srila Prabhupadas purport to Bhagavad-gītā 3.13
Watch it here: https://goo.gl/5nxPWS