Anything with strings requires a special touch, whether the person is playing the sensitive viola or a screamin' loud electric guitar. To produce sound on a stringed instrument you must vibrate it's strings and there are three common ways to do this.
"Plucking" creates a sound by use of either finger, thumb or pick. The guitar. banjo, mandolin, and dulcimer are familiar examples. "Bowing" involves drawing a bow across the strings as you would with the cello or any of the instruments in the violin family. And finally "striking" creates sound when the strings are struck with a hammer. The hammered dulcimer is one example and the piano (also considered a percussion instrument) is another since the mechanical action on it's keys produces pounding on it's strings.
SAMPLE SOUNDS: VIOLIN | VIOLA | CELLO | BASS