add midi pitch bend to arduino sketch

I have a captivate sensor usb class compliant device which is programmed with a basic arduino sketch to send midi notes, and acts as a midi bagpipe controller, different finger combinations sends different notes I would like to add vibratto using pitch bend, either as a filter or a pitch decrease of about -10, the sketch uses a fingering file that defines the midi note. the sketch is here [login to view URL]