Monica Jones asked about the propulsion units on the organs shown in
230919 MMDigest. Look carefully at minutes 2 through 4 of the video:

https://www.youtube.com/watch?v=j34Hudcgwpc
 
Draaiorgel festival Amsterdam 2 september 2023

You will see a variety of power units as the videographer rushed through
the Dam. At least one organ is on a typical trailer pulled by a car, but
many are self-propelled.

I haven't seen this type of unit before. In the past I think a motorized
unit was used under the trailer hitch and the operator walked ahead,
leading the organ.

The units are sort of an "outboard motor" swiveling through 360 degrees.
Most have a gasoline engine and chain drive. Some may be electric. They
are mounted behind a standard trailer hitch.

The road transport truck or trailer would be parked off-site and the
swivel unit used for positioning in restricted spots.

Wallace Venable