Combining electrically the signals from microphones, tape, and reproducers and other sources.
"I just played the tape my Dad made in 1942 to my now 91year old Dad and 88 yr old Mom... It was a wonderful slice of family history to listen too. Backstory: My Dad was 21yrs old in November 1942. RAF pilot in-training --sent to Western Canada -- during a leave break he traveled to Seattle. David Beck's Teamsters (yes that David Beck) offered a ..."