In the early part of the 20th century August Stroh developed a variety of mechanically amplified string instruments, including Ukuleles, using technology borrowed from the new phonographic industry. As always with new chordophone technology in the period the reason was to try and make the instruments louder to compete with the Brass and Woodwind. The horn idea had one other useful function though, it gave a much more directional sound that could be directed toward the recording devices of the time, (as this was when musicians played and sang into the big end of a megaphone, which concentrated the sound at the stylus as the machine cut a record directly). The technology used on Stroh's instruments appear to have been a major influence on John Dopyera and the later development of his resonator Instruments. 

August Stroh, using the brand name Strohviols, whilst a major producer of the Horn Resonator Ukuleles was not the only one. A.T. Howson of London started producing one string fiddles based on a similar concept in 1906 and went on to produce at least one Ukulele variant