Hupka took thousands of photographs, secretly or not, of conductor Arturo Toscanini while Toscanini was leading the NBC Symphony Orchestra. The greatest of these were published in the book This Was Toscanini, (1963) accompanying an uncompleted essay by Samuel Antek, a violinist in the NBC Symphony. Later, those and more photos were used as cover art for Toscanini reissues on LPs and CDs. In the late 1980s, he worked with engineers at NBC International on the audio/video synchronization of the Toscanini telecasts, which were finally issued by BMG/RCA in the early 1990s.