Haggin was a staunch but not entirely uncritical admirer of the conductor Arturo Toscanini. Their personal friendship lasted from the late 1930s, shortly after Toscanini started conducting the NBC Symphony, which the network had enlarged from its house orchestra for him, on Christmas night 1937, to 1950, four years before Toscanini's retirement. He was the first major American critic to recognize choreographer George Balanchine. Also in the 1930s, he launched the career of the future record producer John Hammond, hiring him as a reviewer for the "Brooklyn Daily Eagle".