The Pitch Bend Change message is normally sent from a keyboard instrument in
response to changes in position of the pitch bend wheel. The pitch bend
information is used to modify the pitch of sounds being played on a given
Channel. The Pitch Bend message includes two data bytes to specify the pitch
bend value. Two bytes are required to allow fine enough resolution to make pitch
changes resulting from movement of the pitch bend wheel seem to occur in a
continuous manner rather than in steps.
The two bytes of the pitch bend message form a 14 bit number, 0 to 16383. The
value 8192 (sent, LSB first, as 0x00 0x40), is centered, or "no pitch
bend." The value 0 (0x00 0x00) means, "bend as low as possible,"
and, similarly, 16383 (0x7F 0x7F) is to "bend as high as possible."
The exact range of the pitch bend is specific to the synthesizer.