String bending
String bending is a guitar technique where fretted strings are displaced by application of a force by the fretting fingers in a direction perpendicular to their vibrating length. This has the net effect of increasing the pitch of a note. String-bending allows exploration of microtonality and can be used to give a distinctive vocal articulation to lead guitar passages.
String bending is executed by fretting a note on the guitar fretboard, and then applying a force perpendicular to the length of the fretboard with the fretting hand, displacing the string from its resting vibrating position. This yields a continuous increase in pitch, which can be manipulated by a skillful player to give a singing-like quality to a musical passage. The displacement of the string can be pushed "up" or pulled "down". Bending is an important component in the style of several renowned players, such as Eric Clapton, who uses copious amounts of string bending to articulate blues licks. Jimi Hendrix used the string-bending intro for "Foxy Lady". String-bending blues-scale guitar solos were used in 1950s electric blues music, from where rock musicians later adopted the string-bending technique in the 1960s.
There are numerous mechanical and acoustic properties which heavily influence the resultant pitch from a string bend. Analysis of the physics of string bending suggests that the resultant pitch of a string bend is given by
...
Wikipedia