Frank Sinatra's 1967 recording of "The World We Knew (Over And Over)" was regarded by his own producer as a genuinely difficult song to sing, despite Sinatra's reputation for effortlessly reinterpreting standards. The track, written by German composer Burt Kaempfert, followed on from Sinatra's hit "Strangers in the Night" from the previous year, and producer Jimmy Bowen later revealed that Sinatra relished the challenge rather than being deterred by the song's tricky melody.

According to Bowen, quoted in the biography The Song Is You, Sinatra used to laugh about how "testy" Kaempfert's melodies were, acknowledging that both "Strangers in the Night" and "The World We Knew" were hard to sing well. Despite this, Sinatra pulled it off, though the single peaked at a modest number 30 on the Billboard chart while topping the easy listening chart for five weeks; the same album also produced "Somethin' Stupid", which became a transatlantic number one.