A control on a synthesizer which raises or lowers the pitch of the notes being sounded. (Also referred to as "pitch bend", "bend lever", etc.) The pitch wheel, usually found at the left end of the keyboard, often takes the form of a large thumbwheel, mounted such that the direction of motion is front-to-back,. (A notable exception is Roland synths, most of which use a device called the pitch stick that combines the pitch and mod wheel fuctions; the stick moves left and right for pitch bend.) Generally the wheel is spring-loaded so that it returns to the center neutral position when released, and a center detent is provided. On most modern synths, the pitch range of the wheel can be programmed as part of the patch; older units usually have a fixed range of ± one octave. This is intended as a performance control, as opposed to a tuning mechanism.
Pitch wheel also refers to a MIDI message type which conventionally is sent by the transmitting unit when the pitch wheel is moved, and is interpreted by the receiving unit as a request to alter the pitch. Unlike Modulation, the Pitch Wheel message is not a Continuous controller instance; it is a separate message type. The message always sends two data bytes, but many older synths have less than 14 bits of pitch wheel resolution and always zero out the lower-order bits.