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.

Technique

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.[1] 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 [2] who uses copious amounts of string bending to articulate blues licks. Jimi Hendrix used the string-bending intro for "Foxy Lady".

Factors influencing string bending

There are numerous mechanical and acoustic properties which heavily influence the resultant pitch from a string bend. Analysis of the physics of string bending [3] suggests that the resultant pitch of a string bend is given by

\nu = \frac{1}{2L} \sqrt{\frac{T + \cos\theta (T - EA)}{\mu_{o}}}

where L is the length of the vibrating element, T is the tension of the string prior to bending, \theta is the bend angle, E is the Young's Modulus of the string material, A is the string cross sectional area and \mu_{o} is the linear density of the string material.

Thus, the pitch is not only dependent on the bend angle, but on material properties of the string such as Young's modulus; this may be interpreted as a measure of the stiffness of the string. The force required to bend a string to a given angle \theta is given by

F_{B} = \left(T + EA\left(\frac{1 - \cos\theta}{\cos\theta} \right) \right)\sin\theta .

It is important to note that the resultant pitch from string bending is not linearly correlated with the bending angle, and so a player's experience and intuition is important for accurate pitch modulation.

References