next two years he worked on the machines constantly, modifying them and improving their performance. His main hope was to interest the Hollywood movie studios in using magnetic tape for movie sound recording. Stateside Career Mullin gave two public demonstrations of his machines in Hollywood in 1947, in which he first presented live music performed behind a curtain, followed by a concealed playback of the performance. Mullin's recorder caused a sensation among American audio professionals and many listeners could not tell the difference between the recorded and live performances. By luck, Mullin's second demonstration was at MGM Studios in Hollywood and in the audience that day was Bing Crosby's technical director, Murdo Mackenzie. Mackenzie arranged for Mullin to meet Crosby, and in June 1947 Crosby was given a demonstration of Mullin's magnetic tape recorders. Crosby was impressed by the amazing sound quality and instantly saw the huge commercial potential of the new machines. Up to this time, most pre-recorded programming such as serials and drama were produced on disc, but live music was the standard for American radio at the time and radio networks tightly restricted the use of music on disc because of the comparatively poor sound quality. Crosby, who was arguably the biggest star on radio at the time, was very receptive to the idea of pre-recording his radio programs. He disliked the regimentation of live broadcasts, and much preferred the relaxed atmosphere of the recording studio. He had already asked the NBC network to let him pre-record his 1944-1945 series on transcription discs, but the network refused, so Crosby had withdrawn from live radio for a year and returned for the 1946-47 season only reluctantly. Crosby realised that Mullin's tape recording technology would enable him to pre-record his radio show with a sound quality that equalled live broadcasts, that these tapes could be edited precisely, and replayed many times with no appreciable loss of quality. Mullin was asked to tape one show as a test; it was a complete success and Mullin was immediately hired as Crosby's chief engineer to pre-record the rest of the series. Crosby became the first major music star to master commercial recordings on tape, and the first to use tape to pre-record radio broadcasts. The shows were painstakingly edited to give them a pace and flow that was wholly unprecedented in radio. Mullin has claimed that he even pioneered the use of