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 the instrument has been revived, musicians have used it in a variety of styles of music (see the list of recordings that use hurdy-gurdy), including contemporary forms not typically associated with it. In the eighteenth century, the term "hurdy-gurdy" was also applied to a small, portable "barrel organ" (a cranked box instrument with a number of organ pipes, a bellows and a barrel with pins that rotated and programmed the tunes) that was frequently played by poor buskers (street musicians). Barrel organs require only the turning of the crank to play; the music is coded by pinned barrels, perforated paper