in Europe. Hedy and Mandl married in 1933. During her marriage which broke up in 1937 she, as Madam Mandl, an institution in Viennese Society, entertained foreign politicians like Hitler and Mussolini who were stunned by her beauty. In his armament works Mandl specialised in producing shells and grenades, but from the mid-thirties onwards manufactured military aircraft as well. He was also interested in control systems and did some research in this field. Hedy obviously learned about these matters talking to her husband and listening to his conversations with visitors.²⁸

Antheil was one of the avant-garde composers of his time, writing and playing machine-like, ‘mechanistic’, rhythmically propulsive pieces like the ‘Airplane Sonata’, the ‘Sonata Sauvage’, ‘Death of Machines’, and ‘Jazz Sonata’.²⁹

George was a specialist in scandals. His ‘Ballet mécanique’ was scored for 16 pianolas, xylophones and percussion and was first performed in Paris in June 1926 in a reduced version for one pianola, but with electric bells, aeroplane propellers, siren etc. The pianola will play an important role later in our story.

In the late summer of 1940 Hedy Lamarr, who lived in Hollywood not far from Antheil’s house, contacted him. In her conversation with Antheil she also brought up the idea of torpedo radio control.³⁰

The general idea was not new. What was at least fairly new was the idea of ‘frequency hopping’ which is nowadays used extensively in military communications: a signal is broadcast over a seemingly random series of radio frequencies, rapidly switching from frequency to frequency at split second intervals. The signal could carry commands for directing a torpedo. A receiver, hopping between frequencies in synchrony with the transmitter, could pick up the message so that possible eavesdroppers could hear only random blips. Attempts to jam the signal – jamming signals was and is one of the drawbacks of radio control – could, however, only knock out bits of them, but this could be sufficient to reach the objective. It was Hedy Lamarr who communicated the idea to George Antheil. Antheil’s contribution was to suggest a device by which synchronisation could be effected: synchronising a series of rapid changes in radio frequencies would be no more difficult than synchronising player pianos as in his ‘Ballet méchanique’ of 1926, scored for 16 synchronised pianos.³¹ Indeed, the patent for which they applied on 10 June 1941 ’Secret Communication System’ specifies the use of slotted paper rolls – similar to piano roles – to synchronise the frequency switches in the transmitter and receiver. It is also significant that the number of frequencies proposed – 88 – matches exactly the number of keys on a piano. Putting the idea into practise was, however, a different matter. In spite of the allegedly enthusiastic endorsement there was a lot of scepticism. One of the examiners at the Inventor’s Council, for example, doubted if the clock work mechanism suggested for moving the perforated tape would provide sufficient accuracy.