MainStage MIDI preferences
These preferences let you view the current status of MIDI inputs and choose which note appears as middle C.
MIDI
MIDI Status field: Displays the number of detected MIDI inputs.
Setup button: Click to open the Audio Devices pane of Audio/MIDI Setup Utility.
Display
Display Middle C pop-up menu: Choose whether middle C is displayed as C3 or C4.
Program Change Range pop-up menu: Choose whether program changes use the range of 0–127 or 1–128.