What happens when you tighten a guitar string by turning its keys what pitch will make?

When you tighten a guitar string by turning its keys, you increase the tension in the string. This higher tension will cause the string to vibrate at a higher frequency, producing a higher pitched sound. Conversely, loosening the string will reduce the tension and result in a lower pitched sound. The pitch of a musical note is directly related to the frequency of the vibration, with higher frequencies corresponding to higher notes and lower frequencies corresponding to lower notes.