> I think there was a system which recorded a track, reversed the
> tape in a hurry and then recorded another one parallel to it and
> so on. I cannot remember who made it, possibly Loewe-Opta.

I worked on the design of one such that used a tape cartridge similar
to the 3M DC-300 (a little bigger than a cassette).  It had a tape
acceleration of 20,000 inches/second/second and could reverse direction
during the vertical retrace interval.  Never was practical to produce,
though.

Marc Kaufman