The sound of Operation Amsterdam

[Bob Essex]

The wonderful sound of the pierment organ prompts me to ask a question. How do they manage to achieve that particular haunting sound?

Does anyone among our organ-building friends know the answer.

I seem to remember one of my many videos has a Dutch organ builder explaining that a particular bell-like ringing sound is achieved by adding a rank playing minor thirds in unison, I think. Is that what this sound is?
It certainly doesn't sound like violin pipes.

I tried this once, but the result was dreadful, and I used the pipes for something else.

Bob Essex