Violin, guitar, cello, banjo are all stringed musical instruments. The sound in them appears due to the vibration of the stretched strings. There are bowed and plucked strings. In the first, the sound comes from the interaction of the bow and the string - the friction of the bow hair causes the string to vibrate. Violins, cellos, violas work on this principle. Plucked instruments sound due to the fact that the musician himself, with his fingers, or with a plectrum, touches the string and makes it vibrate. Guitars, banjos, mandolins, domras work exactly on this principle. Note that sometimes some bowed instruments are played with plucks, achieving a slightly different timbre. Such instruments include violins, double basses, and cellos.