Thank you, Tony! The recent photo was taken using a feature available on OM System OM-1 called "Live Composite."
Essentially, the camera captures the background with a single base exposure and then overlays only the new light sources that move through the frame afterward. You can see the image developing in real time in the camera display and you interrupt the process whenever you are satisfied with the result.
In this photo, the background also shows motion blur due to ICM.