He was a student of the Italian tenor Tito Schipa. Kelen had sung to ovations in Budapest and throughout Europe as a guest performer.
Though he was known as a lyric tenor, he had sung many a heroic tenor roles with great success. Kelen emigrated to Canada in 1967 and became a freshman member of the New York City Opera in 1969.
In the same year, he won the first Morton Baum Prize as the singer showing most promise in the company.
Giving up his opera career, he went on to pursue a career as a cantor at Temple Beth El in Cedarhurst, New York where he served for over twenty years.
He died at the age of 63 in Saint John’s Hospital in Far Rockaway, Queens, following a stroke.