Picking up Wayne Stahnke`s comment on the spelling of disc, I have
understood the situation to be that disks can be written upon whereas
discs cannot. Therefore musical box discs would be discs, but computer
disks would be disks. We differenciated between the two in the BBC
because disks (so called `acetates`) had a different level and different
playback characteristic to discs, which were commercial pressings.

Best wishes to all,

Robin Cherry