Isepp was born in Vienna, where his parents were well connected in the city’s arts scene; his mother was singer Helene Isepp and his father, Sebastian Isepp, was an expert art restorer and a gifted painter. They fled Austria in 1938 and settled in Britain, where Martin studied piano and conducting at the Royal College of Music and served in the Royal Army Service Corps. In 1957 he was invited to join the staff at Glyndebourne where he worked in various capacities, including head of the music staff, for more than 40 years. 

Isepp was on Juilliard’s Vocal Arts and Literature and Materials of Music faculties from 1973 to 1977, when he left to become the head of the newly formed National Opera Studio, a position he held until 1995. At Juilliard, he was the head coach in the opera training department and among the productions he conducted were Britten’s The Turn of the Screw in 1975 and Cimarosa’s Il matrimonio segreto, in 1976. 

Among the singers Isepp accompanied over the years were Janet Baker (who had been a student of his mother’s), Victoria de los Angeles, John Shirley-Quirk, Maureen Forrester, and Jessye Norman. “An accompanist’s life will never be an easy one, but I like it,” Isepp told The New York Times in 1975. “I never thought I’d do anything else.” 

Vocal Arts faculty member Steven Blier recalled his former teacher:

Martin Isepp was a teacher of mine at a crucial moment in my life. When I was 20, I enrolled in the Extension Division at Juilliard to work with him (at the insistence of Matthew Epstein, the former director of Columbia Artists Vocal). That one semester was the only time I was ever enrolled in a music school, but those three months did a great deal to set the course of my life. Martin helped to tune my ear, he boosted my confidence, he showed me what a professional collaborative pianist did, and thought about, and knew—and gave. In order to continue our lessons, he got the administration to take me on as a staff pianist so that I’d have a Juilliard ID—another enormous opportunity. I still think of Martin when I play Brahms and Mahler and Schumann—he is inextricably woven into the fabric of “Von ewiger Liebe” and Dichterliebe. I have always been grateful to him for his steadying hand when I was very young. Requiescat, Martin. May Victoria de los Angeles and Margaret Price serenade you in heaven.