He became secretary of the tenor Jan Kiepura and they both emigrated to the United States when persecution of the Austrian Jews became unbearable in the late 1930s.
He became widely known and highly regarded because of a television and radio broadcast series produced by the ORF, where he introduced his viewers and listeners to the world of opera and operetta with outstanding knowledge and great humor.
Prawy maintained close friendships with many prominent singers, composers and musicians, such as Leonard Bernstein and Robert Stolz.
In his final years, Prawy was quite frank about his unique, and rather eccentric, method of archiving his enormous collection of theatre programmes, recordings, letters, photographs, personal notes, and similar loose sheets gathered over many decades.
Although Prawy lived in a room at the Hotel Sacher, he invited journalists into the private apartment he was still keeping: it contained thousands of plastic shopping bags, each of which was carefully labelled so that he could readily access any information he needed.