I am sorry to hear of the passing of a person with of a wealth of
knowledge about music boxes.  I have never been to Utrecht, but
was introduced to it through the YouTube video by Wintergatan about
their Marble Machine.  They just posted 21 new videos of various
instruments at the Museum Speelklok to add to 23,000 videos that
come up when searching for the Museum Speelklok.  Here is a link to
one of them:  https://www.youtube.com/watch?v=o3SecHzbN2E 

While these videos provide a sense of these instruments, there is
nothing like actually seeing and hearing these instruments in person
with someone who really knows them thoroughly.

Thank you for telling us about Luuk Goldhoorn.

Patrick Daniels