Before Beatles became a phenomenon, Western pop meant American pop.
American pop was interestingly diverse by nature. In each period, the mainstream was never the only sound on offer. In the 1950s, because of the general prosperity of the American music market, the co-existence mainstream and subcurrents was even more tangible. The music that travelled to Hong Kong then exhibited the same pluralistic tendencies. Amidst these, some stars shone.
In the 50s, the dominance of big band and swing music in America had gone. In their place was a trend favouring star vocalists singing broadly slow-tempo ballads, often expanding upon the Tin Pan Alley standards. New singers joined established ones. Together they brought about the golden age of the vocalist tradition.
Wong Jum-sum looked to the West at this time. He met those golden stars, and never looked back.