He then became assistant conductor to Leonard Bernstein at the New York Philharmonic.

NPR: Conductor James DePreist

In 1957 he was appointed to his first full-time job, as assistant conductor of the BBC Scottish Orchestra (now the BBC Scottish Symphony Orchestra).

BBC: Obituary: Colin Davis

Should Mr. Levine be unable to conduct on any given night, an assistant conductor would be ready to step in a standard protocol for all Met performances, regardless of the maestro, said general manager Peter Gelb.

WSJ: Met Opera Maestro James Levine Marks Return in Small Steps