How does a guitar with six strings wired across a long-neck wooden box produce notes, rhythm, melody and music? Plucking a string creates the standing waves by vibration, which further compresses the surrounding air into sound waves. Some points on the string, called nodes or anti-nodes, oscillate back and forth. Sound waves mostly escape through the hole, translates them into electrical impulses and then your brain interprets as sound. Four things affect the frequency of a vibrating string:the length, the tension, the density and the thickness. When two strings are struck together, the added-up waves can form a chord if the frequencies come in harmony.