String bending

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. 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.

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 suggests that the resultant pitch of a string bend is given by

ν = 1 2 L T + cos ⁡ θ ( T − E A ) μ o

where L is the length of the vibrating element, T is the tension of the string prior to bending, θ is the bend angle, E is the Young's Modulus of the string material, A is the string cross sectional area and μ 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 θ is given by

F B = ( T + E A ( 1 − cos ⁡ θ cos ⁡ θ ) ) sin ⁡ θ .

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.