Vibrato. It’s the same in vocals, changing pitch quickly in a way that sort of sounds like a vibration, though the technique itself is not called vibration.
Melchior Broederlam was heavily influenced by the Trecento style of painting. Trecento style was created during the Renaissance era. It centers on the Italian culture.
Broederlam was able to demonstrate his style by making panel painting of the Christian culture. Broderlam was said to paint a panel painting of the Flight to Egypt, Presentation in Jerusalem and the Annunciation and the Visitation.