A fourth-generation Christian, Barathi is the son of E. Soundararajan (1932–1997), a Presbyterian pastor in Chennai for 47 years, and Ruby Viruthambal, and husband of Evelyn Priscilla Vasanthi.
In 1986, he earned a Bachelor of Arts in psychology (and passed Grade VIII Classical Guitar, Trinity College Exams at the Chennai Local Center). In 1989, he completed a Bachelor of Arts in Church Music from the Asian Institute for Liturgy and Music in Manila, Philippines.
By 1992 he was back in India, where he married Evelyn; their first son Jasperraj was born while John was a music lecturer in Nagaland. John was teaching music in the public schools when their daughter Jenita was born in 1996.
In 2002, he earned a Master of Arts in Church Music from Tainan Theological College, Taiwan. The same year he joined the Church of South India (CSI) Synod as the Coordinator for Church Music & Liturgy, where he was working as of 2019.
Barathi is presently engaged in a project to produce a
Common English Hymnal for the CSI. A diverse, multi-cultural organization, the CSI has multilingual and varied ethnic congregations spread over almost half of India, plus global congregations.
His English translations of more than 200 Christian Tamil hymns, songs, original choral works, transcriptions and compositions of different genera can be found at free-scores.com.