Found a 1980 brochure for AlphaSyntauri on archive.org:
https://archive.org/details/TNM_alphaSyntauri_live_music_on_Apple_computer_-__20180131_0046

I think they mean from C to C not F to F.
Wikipedia says "The modern console specification recommended by the American Guild of Organists calls for manual keyboards with sixty-one notes (five octaves, from C to c′′′′)".

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