Just some thoughts for the >swell door<
I have seen some of the harps with removed >doors< but than it is visible
by the groove and slot for the pedal at the harp base.
The swell doors have a effect for loudness…but not that much one would expect.
Other thoughts are going to deep in to mystical speculation.
The harp body of this harps have only the sound holes at the back, when you close them with the swell doors you just set the vibration inside the harp in to