 In the summers of 1960 and 1961, he served as a coach and assisted Hans Knappertsbusch at the Bayreuth Festival, and in 1961 was assistant conductor to Ferenc Fricsay for the Salzburg Festival production of Mozart’s "Idomeneo".He continued to assist Fricsay both in Salzburg and in Berlin with the RIAS Symphony Orchestra and Deutsche Grammophon through 1964.In 1965, Erős came to the United States for the first time at the invitation of George Szell to work with him and the Cleveland Orchestra as a Kulas Foundation Fellow.