The Stroh violin or Stroviol is a type of stringed musical instrument that is mechanically amplified by a metal resonator and horn attached to its body.

[1] The name Stroviol refers to a violin, but other instruments have been modified with the amplification device, including the viola, cello, double bass, ukulele, mandolin, and guitar.

[citation needed] Johannes Matthias Augustus Stroh, an electrical engineer from Frankfurt, invented the instrument in London in 1899.

[2] On 4 May 1899, Stroh applied for a UK patent, GB9418 titled Improvements in Violins and other Stringed Instruments which was accepted on 24 March 1900.

[3] On 16 February 1901 he applied for a second UK patent, GB3393 titled Improvements in the Diaphragms of Phonographs, Musical Instruments, and analogous Sound-producing, Recording and Transmitting Contrivances which was accepted on 14 December 1901.

His failure to register his inventions in the USA allowed John Dopyera and Geo Beauchamp to subsequently obtain US patents for the tricone and single cone designs used in National brand instruments.

A number of musicians, including Tom Waits, Carla Kihlstedt, Thomas Newman, Bat for Lashes, A Hawk and a Hacksaw[4] and Eric Gorfain continue to use the Stroh violin for its distinctive sound.

Shakira featured a Stroh violin on her 2010/11 The Sun Comes Out World Tour, with multi-instrumentalist Una Palliser playing it on some songs.

Kagel found a photograph dated 1910 of a small instrumental group in a recording studio which includes three Stroh violins.

The horn-violin is harder to play than a normal violin because the reaction of the bow on the strings is less flexible, and the instrument's weight is less evenly distributed.