John Mullin was in the Army Signal Corps during World War II and in 1945 he was sent to Frankfurt to investigate reports that the Germans were using high frequency energy to jam aircraft engines. He found Magnetophon in Radio Frankfurt, 45 miles north of Frankfurt in Bad Nauheim. Mullin sent 2 machines to San Francisco as war souvenirs inside 35 regulation mailbags. He reassembled the machines in early 1946 and gave a demo in May 1946 at the IRE meeting in SF, using pipe organ music recorded from KFRC with his partner Bill Palmer. Mullin and Palmer used the tape recorder for film soundtracks. At the demo he met Harold Lindsay. In June 1947 Mullin gave another demo to Bing Crosby. He met Murdo McKenzie, tech producer for Crosby. Mullin was invited to record the first show of the 1947-48 season and Mullin taped and edited that first show. Mullin used his 2 Magnetophons and 50 reels of tape to do 26 Crosby shows in 1947. Each reel had a 22-minute play time. The iron particles were imbedded in the plastic tape rather than coated on the surface, and volume would change with the differenct thickness of the tape, the thicker tape producing louder volume of low frequencies. Mullin recorded the afternoon rehersals as well as the evening show before an audience, and edited the final show from these tapes. The Ampex tape recorders arrived in April 1948, Model 200 serial numbers 1 and 2. ABC received 12 more recorders immediately after. In fact, the ABC order had financed the development of the first 2 recorders. They were used to edit the 27th Crosby show of the 1947-48 season. Mullin added a laugh track to some of Crosby's routines, thus giving birth to the laugh-track.
John Mullin recorded a videotape in 1989 for the Audio Engineering Society ("An Afternoon With John T. Mullin" in VHS or PAL cassette from AES Publications). He demonstrated his own collection of recording machines, including a Vitaphone disk cutting lathe of 1927.