In 1942, Kestenberg hired him as an orchestra substitute and, just a year later, he was appointed a full member of the orchestra.
The two came into closer contact when Steinberg attended Kestenberg's course on the aesthetics of Bach's two-part inventions, which was free of charge. During his time as General Manager, Kestenberg continued to pursue activities in music pedagogy, though not publicly. He worked with small study groups and gave his first private piano lessons.
Also among the course participants were the pianist Menachem Pressler and Ella Goldstein, who took private piano lessons with Kestenberg from the end of the 1930s to the mid-1940s.