1920s Horned Stroh Violin
The Stroh violin has two horns, one positioned at the end of the fingerboard to project the sound to an audience or recording horn, and a smaller monitoring horn that allowed the player to hear their own sound more clearly.[1]
The Stroh violin is much louder than a standard wooden violin, and its directional projection of sound made it particularly useful in the early days of phonographic recording. Wooden violins recorded poorly with the early acoustic-mechanical recording method, and the Stroh violin improved this by producing a fuller, louder sound.
Stroh violins were common in recording studios, but became rarer after record companies switched to the new electric microphone recording technology in the second half of the 1920s