Landau founded the Brooklyn Philharmonia (later the Brooklyn Philharmonic) in 1955, an orchestra of freelance musicians in the New York City area with a focus on contemporary or infrequently performed classical music. His tenure as the orchestra's first music director was from 1955 to 1971, when he resigned after the orchestra had reduced its season and programming opportunities during a period of financial difficulty. From 1961 to 1981, he was the conductor of the Music for Westchester Symphony (later the White Plains Symphony), until he left the orchestra over disputes with the board of directors regarding programming. He led the Chattanooga Opera Association from 1960 to 1973. In Europe, he was Generalmusikdirector of the Westphalian Symphony Orchestra from 1973 to 1975.
Landau's compositions included music for a dance drama, The Dybbuk, by Anna Sokolow. Landau was also a teacher at the Jewish Theological Seminary and the music director for Shearith Israel Synagogue, Manhattan.
Landau married Irene Gabriel in 1954. They had two sons, Robert and Peter. Landau often conducted the music for Gabriel's dance company in the 1950's and 1960's. Landau and Gabriel moved into their Brushton home in upstate New York in the 1970's.. They died in a fire which destroyed the residence. Their sons survive them.