Zygmunt Mycielski met him in the editorial board of Przegląd Kulturalny in the 1950s, and when in 1957 Ruch Muzyczny was revived, Mycielski had Erhardt joined the journal’s editorial team. From then on the two men worked together. When in 1960–68 Mycielski served as the journal’s editor-in-chief, Erhardt was his right hand. After Mycielski’s dismissal Erhardt was put in charge of the journal, though he was not formally made its editor-in-chief until 1971. He held this position until 2008. Years later the publishing company he founded published letters which Mycielski sent to him and to the editorial board of Ruch Muzyczny. He finished his tribute to Mycielski in the following manner:

Without Zygmunt Mycielski Ruch Muzyczny could have been published but could not have existed ("Listy Zygmunta Mycielskiego do Ludwika Erhardta i redakcji «Ruchu Muzycznego» 1957–1986", Warsaw 2014)