Devassy's first major break came when he was aged 18, through Johny Sagarika, for whom he did the music orchestration of six songs on the album Ishtamannu. He then went as an accompanying artist to play the keyboard for Hariharan on his European tour. He has also accompanied the violin maestro L. Subramanian at the Lakshminarayana Global Music Festival
At age 19, he started a music band called Seven, with singers Franco Simon and Sangeeth Pavithran. A Hindi pop band, they released an album titled Yeh Zindagani.Stephen, who started performing at a young age, has done the music arrangement for many films. Some of the films he scored were Majaa, Thambi, Nammal, Azhagiya Thamizh Magan and Hariharan's album, Waqt Par BolnaHariharan Pilla Happy Aanu (2003) was his maiden music directorial venture in Malayalam.Lyrics was written by Famous young lyricst Rajeev Alunkal.All songs in this picture is still super hits.
Umayal Puram Sivaraman learned the art of the carnatic mridangam from four illustrious masters of the art - Sri Arupathi Natesa Iyer, Sri Tanjavoor Vaidyanatha Iyer, Sri Palghat Mani Iyer & Sri Kumbakonam Rangu Iyengar. The pursuit of this art under the gurukula system for well over fifteen years did not deter him to qualify for law, and he graduated from The University of Madras with a B.A. & B.L..
He has accompanied several top ranking Carnatic and Hindustani musicians in their concerts, such as Sri Ariyakudi Ramanuja Iyengar, Sri Chembai Vaidyanatha Bhagavathar, Sri Musiri Subramania Iyer, Sri Palladam Sanjeeva Rao, Sri Mysore Chowdiah, Sri Rajamanickam Pillai, Sri Papa Venkataramiah, Sri Dwaram Venkataswami Naidu, Sri Mudikondan Venkatarama Iyer, Sri G. N. Balasubramaniam, Sri Madurai Mani Iyer, Sri Maharajapuram Viswanatha Iyer, Sri Alathur Brothers, Dr Semmangudi Srinivasa Iyer, Dr M. Balamuralikrishna, Sri Palghat K.V Narayanaswamy, Sri Nedunuri Krishnamurthi, Sri Voleti Venkateswarulu, Sri S. Balachander, Sri T.R. Mahalingam, etc. He has to his credit several jugalbandhi concerts with the top artistes of Hindustani music like Pt. Ravishankar, Sri Hariprasad Chaurasia, Pt. Ram Narain and top tabla artistes like Pt. Kishen Maharaj, Pt. Samta Prasad, Ustad Allah Rakha, Mr. Zakhir Hussain and others. He has trained many students in the art of mridangam and continues training more disciples.