Hello Charlie,
Welcome to the forum.
Please try:
- Load the MasterWorks 3-31 organ.
- Use the General Cancel (e.g. click on the 'C' virtual piston) to turn off all stops.
- Turn on just the Clarinet 8 stop on the Great.
- Play and hold chord from your MIDI keyboard on the Great virtual keyboard.
- Whilst holding that chord, use the mouse to drag the left-most virtual expression pedal ("Main Pedal") vertically back and forth between its 'fully closed' to 'fully open' positions.
- Do you hear the effect of the swell box upon the Clarinet rank, as you should?
- Stop playing the chord.
- Now use right-click auto-detection on that left-most virtual expression pedal ("Main Pedal"), being careful during auto-detection not to touch any other MIDI controls/pedals, whilst also ensuring that you move the MIDI pedal back and forth several times across its full compass (so that its full range is 'heard' by Hauptwerk), then click 'Done' on the auto-detection screen.
- Now play and hold the chord on the Great again.
- Move that MIDI expression pedal back and forth across its full compass.
- Do you hear the same effect of the swell box upon the Clarinet rank, as you did previously above when using the mouse to move that virtual expression pedal?