Elektor: 1978 June
This June 1978 issue includes an article announcing the new Elektor Software Service. The magazine had been publishing short programs for the SC/MP system but realized that the programs were taking up too much magazine space (hey, you need to make room for the ads). In addition, when you have to enter the programs by hand, it takes a LOT of time and you can easily make a mistake and ruin the whole program. The editors considered printing the programs as a series of barcodes but that still would have taken a fair amount of magazine space and the reader would have needed a special "light pen" to read the barcoded programs.
To solve the problem, they chose what you and I might view as an unusual medium to deliver their software programs. They didn't use papertape, they didn't use punchcards, they didn't use audio cassettes (although they considered them) and they didn't use floppy discs. Instead they used 45 RPM records. Yep, they put the software programs on vinyl. Imagine, you could send away to England and get a digital clock program on one side of your 45 record and then turn it over and play the Beatles' "I want to hold your hand" on the other side. (OK, I made up the part about the Beatles.)
As the magazine states, "It seems an obvious choice to record data on the discs in the form of an FSK (frequency-shift-key) signal to CUTS standard (300 baud, 0=8 cycles at 1200Hz, 1=4 cycles at 2400Hz)." Yep, obvious!