Wikipedia
Violectra is the trade name of an electric violin produced by Barcus-Berry with the pitch equivalent of an acoustic tenor violin, sometimes called baritone violin. It is tuned an octave below normal violin, i.e. between viola and cello. It was developed in USA by Barcus-Berry in the early 1960s. Jean-Luc Ponty, MichaĆ Urbaniak and Elek Bacsik were among the first famous jazz violinists to play it. Fiddler Vassar Clements brought the instrument into the progressive bluegrass scene, and Urban Blitz into a rock music context.
The first recording known of with it is by the maker himself John Berry on a 1963 demonstration album.
Violectra is nowadays the name of a range of electric violins, violas and cellos designed, developed and hand made by David Bruce Johnson, a Canadian violin maker settled in Birmingham, England. These are the instruments played by Nigel Kennedy and many more professional players worldwide.