String instrument strings, or play them by rolling the bell of a brass instrument such as a trombone on the array of strings. However, these are relatively rarely used special techniques. Other keyed string instruments, small enough for a strolling musician to play, include the plucked autoharp, the bowed nyckelharpa, and the hurdy-gurdy, which is played by cranking a rosined wheel. Steel-stringed instruments (such as the guitar, bass, violin, etc.) can be played using a magnetic field. An E-Bow is a small hand-held battery-powered device that magnetically excites the strings of an electric string instrument to provide a sustained, singing tone reminiscent
Hurdy-gurdy to Vivaldi. At this time the most common style of hurdy-gurdy developed, the six-string "vielle à roue". This instrument has two melody strings and four drones. The drone strings are tuned so that by turning them on or off, the instrument can be played in multiple keys (e.g., C and G, or G and D). During this time the hurdy-gurdy also spread further to Central Europe, where further variations developed in western Slavic countries, German-speaking areas and Hungary (see the list of types below for more information on them). Most types of hurdy-gurdy were essentially extinct by the early twentieth