Crystal frequency control, an essential ingredient in the electronics revolution, was invented in the aftermath of World War I by Walter Cady. Cady exploited his thorough knowledge of a scientific phenomenon called piezoelectricity, on which he gathered expertise during a wartime crash program in submarine detection, the first technological application of the phenomenon. With armistice Cady, a university professor of physics, could change his focus toward open-ended scientific research. He examined results observed earlier in the attempt to utilize piezoelectric crystals, leading him to the discovery of their sharp and steady resonance. Encouraged by professional and personal relationships with corporations and governmental agencies, and by his war experience, Cady followed his findings to design practical devices. Yet he maintained the identity and practices of a physicist, experimentally and theoretically exploring the phenomena further. Like many scientists, he was an occasional rather than professional inventor. This story reveals connections and overlaps but also differences between the kind of research carried out at an industrial research laboratory and at a university.