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 and France, but was largely replaced by the "symphonia", a small box-shaped version of the hurdy-gurdy with three strings and a diatonic keyboard. At about the same time, a new form of key pressed from beneath was developed. These keys were much more practical for faster music and easier to handle; eventually they completely replaced keys pulled up from above. Medieval depictions of the "symphonia" show both types of keys. During the Renaissance, the hurdy-gurdy was a very popular instrument (along with the bagpipe) and the characteristic form had a short neck and a boxy body with a curved tail