Why does the door creak and the violin sings?

The maximum static friction force usually slightly exceeds the sliding friction force, as a result of which the body does not move smoothly, but in a jerk. It is these small jerks that cause creaking in the unlubricated door hinges. But what is annoying at the door fascinates in the violin, the very name of which reveals the “secret” of its sound. When the bow is passed over the strings, due to the action of the friction force at rest, the strings first follow the bow, but then “break”, after which they begin to vibrate – each with its own specific frequency.