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 century, but a few have survived. The best-known are the French "vielle à roue", the Hungarian "tekerőlant", and the Spanish "zanfoña". In Ukraine, a variety called the "lira" was widely used by blind street musicians, most of whom were purged by Stalin in the 1930s (See "Persecuted bandurists"). The hurdy-gurdy tradition is well developed particularly in Hungary, Poland, Belarus and Ukraine. In Ukraine, it is known as the lira or relia. It was and still is played by professional, often blind, itinerant musicians known as lirnyky. Their repertoire has mostly para-religious themes. Most of it originated in the Baroque period.