Born in Kassel, Hartleb first engaged in theatre studies at the Ludwig Maximilian University of Munich and received his doctorate there in 1936.
From 1947 to 1956 he worked in a similar position at the Grillo-Theater in Essen, from 1956 to 1961 at the Oper Frankfurt and from 1961 to 1967 at the Bavarian State Opera in Munich.
[1][2] Hartleb's special domain was modern opera as well as the Italian repertoire.
He was the director of the national premieres of Berg's Lulu in Germany, the Netherlands and Sweden.
[1] In 1967, he directed the world premiere of Eli by Walter Steffens at the Opernhaus Dortmund.