The first truly portable cassette player was the Sony Walkman, invented in 1979, where the user could carry it around and listen to music easily. The machines were just a little larger than the cassette itself. Recorders of that size were also around that timeframe.
When I was judging in the mid-70's, execution judges were not using recorders; they were too bulky at that time. GE judges used cassette tapes first in the box. Analysis judges were switched to tapes when truly portable records came out so they could carry them around at field level.
Guardling is totally correct in his commentary. Execution judging for most of its history had no accountability as to when a judge marked tics. The norm in the 70's was to put a vertical line on the sheet at the end of each tune, so at least the staff knew which song was being judged as the show progressed. In my marching era, there were no analysis judges. Each judge had X number of points for tics, and they had Y number of points for "difficulty", all recorded on the same sheet. In 71, on VFW sheets there were 17 points for ticks and 3 points for difficulty, for instance.
By the time I was judging in the mid/late 70's, execution judges were able to assess group ticks for a particular event. A judge could assign from 1 to 5 tics for a particular event, based on what the judge felt the event deserved.
It was all subjective, only more along the lines of the "death of a thousand cuts" as opposed to the current system.