He and Lamarr were neighbors in the Los Angeles area by this point. The dinner parties of that world were small and interconnected, and at one of them — the date is not precisely recorded, but the research places it in 1940 — they sat next to each other and began a conversation. Antheil later wrote that Lamarr opened the subject of radio jamming, describing the problem of enemy interference with torpedo guidance systems. Torpedoes of the era could be guided by radio signal, but radio control was vulnerable: an enemy ship could broadcast on the same frequency and overwhelm the guidance signal, causing the torpedo to veer off course or detonate prematurely. Lamarr, who had listened to arms-industry conversations for the four years of her marriage to Mandl, understood this as a practical military problem. She had been thinking about it.
What she brought to the conversation was the problem. What Antheil brought was the solution.
His experience with player pianos had given him an intimate knowledge of synchronized mechanical systems running in parallel without direct communication between them. The trick of keeping two pianos aligned — making both machines run so accurately that they tracked the same sequence without anyone on either end monitoring the other — was exactly the principle needed to solve the frequency-hopping problem. If the transmitter on the surface ship and the receiver in the torpedo both carried identical perforated paper strips, driven by identical constant-speed mechanisms, and if both strips began running at exactly the same instant, then both devices would hop to the same carrier frequency at the same instant — without any signal passing between them that could be intercepted.