Professor Kolja Blacher works with the student the first movement of Ysaye's Violin Sonata No. 4, giving instructions about the speed of the vibrato depending on the nature of the passage, the bow's strokes, speed and changes taking into account the dynamics and character (more or less energetic), tension and double cords.
In the end, the professor gives the student some advice on how to train the vibrato: think about in which register may vibrate more or less, and which bowings need more or less energy, as well as the importance of training it slowly.