Floppy-ROM
Back in the early days of computing, common audio cassettes were used to store computer programs before hard disks were created. The Kansas City Standard for encoding binary data with audio signals was created to :
record data as “marks” (one) and “spaces” (zero). A mark bit consisted of eight cycles at a frequency of 2400 Hz, while a space bit consisted of four cycles at a frequency of 1200 Hz. A word, usually one byte (8 bits) in length, was recorded in little endian order, i.e. least significant bit first. 7-bit words were followed by a parity bit.
Someone took the “bits as audio” idea one step further, and decided to try pressing a data phonograph record:
Daniel Meyer and Gary Kay of Southwest Technical Products arranged for Robert Uiterwyk to provide his 4K BASIC interpreter program for the 6800 microprocessor. The idea was to record the program on audio tape in the “Kansas City Standard” format then make a master record from the tape. Eva-Tone made “sound sheets” on thin vinyl that would hold one song. These were inexpensive and could be bound in a magazine.
Bill Turner and Bill Blomgren of MicroComputerSystems Inc. worked with EVA-TONE and developed a successful process. The intermediate stage of recording to tape produced dropouts so a SWTPC AC-30 cassette interface was connected directly to the record cutting equipment.
The May 1977 issue of Interface Age contained the first “Floppy-ROM”, a 33⅓ RPM record with about 6 minutes of “Kansas City standard” audio.
Kansas City Standard: Floppy-ROM: Wikipedia, the Free Encyclopedia