if anyone's interested who downloaded Harsányi's 1951 symphony (premiered 1953) as conducted by Rosenthal back when, I found out more information about the 1956 concert in which that broadcast was performed, etc. See this link (https://catalogue.ina.fr/doc/TV-RADIO/PH_PHD89028879/festival-tibor-harsanyi?rang=15).
Cheers.