Stringed Musical Instruments: How Do They Make Music?
Stringed instruments, such as the violin, have a series of stretched strings on them. When you press down on one of the strings, its length changes and it vibrates at different frequencies, producing varied sounds. A brief stroke on a metallic string produces a loud sound, whereas a long stroke produces mellow music. The thickness of the string is also important, as it controls the strength of the sound.
However, some of the earliest recorded descriptions of hypnosis date back to 1500 B.C. in ancient Egypt.