Pitch bend is the continuous, smooth altering of the pitch of a note in order to add expressiveness or subtlety to music. While prominent in electronic music, it is also used in other forms of popular music and even to some extent in classical music.
Pitch bend is most commonly accomplished by using a pitch bend wheel or lever found on synthesizers and MIDI controllers. It is also used by violinists, who accomplish it by sliding their finger along a string while continuously bowing. It can additionally be accomplished on some other instruments such as guitars and clarinets.
Pitch bend and portamento are closely related. However, whereas the former typically using a pitch wheel or similar controller that can be applied to any note at any time, the latter is an automatic sliding between two consecutive notes that creates a smooth, continuous transition from one pitch to another. It occurs automatically when playing legato.