Music-event in Maastricht

On our trip back from Luxembourg back to Groningen, we visited a friend in Maastricht, in the south of the Netherlands.
That evening there was a music-event with Dutch artists, while at the same time this event was also in Leeuwarden and Haarlem. (with other artists ofcourse and a live video-stream)
This photo shows a crowd, singing along, moving, talking, etc, except for this lady.