The Stroh violin, invented in England by Augustus Stroh, was used in the recording industry from the late 19th century until the introduction of electronic amplification. A standard violin was not powerful enough to record on the wax cylinders whereas the Stroh violin uses a mica resonator and a horn to amplify the sound much like the gramophones of that time. These live on with the Romanians of Bihor who still make them in the villages and call them "vioară cu goarnă" (violin with horn). Other names are vioară cu pilnie (funnel violin), vioară-corn (horn violin).
The D, A, E strings the same as a standard violin, but the G sting (lowest pitch on a standard violin) is replaced by a thinner string just for the mechanical stability of the the instrument. The musicians only use three upper strings.
Alexandru, T (1980), Romanian folk music, Musical publishing house, Bucharest