Pitch-tracking is also known as voice-tracking or pitch-following. In essence it involves acoustic information being received through a microphone. Its output consists of sending pitch data by way of MIDI for further sound processing or triggering.
See also:MIDI, Pitch-to-MIDI
Bibliography: Baird, Bridget, Blevins, Donald, Zahler, Noel (1993). Artificial Intelligence and Music: Implementing an Interactive Computer Performer