ABSTRACT
The vinyl disc as a medium for music delivery in its present form dates back to 1948, when
Columbia introduced microgroove 331⁄3 rpm LP records. These were followed soon after by
microgroove 45 rpm records from RCAVictor. Stereo vinyl did not appear until 1958. The
introduction of Varigroove technology, which adjusts groove spacing to suit the amplitude of
the groove vibrations, using an extra look-ahead tape head to see what the future holds,
allowed increases in groove packing density. This density rarely exceeded 100 grooves per
inch in the 78 rpm format, but with Varigroove 180-360 grooves/inch could be used at
331⁄3 rpm.
