Following the warmup in center with the adage, the ballet class usually moves on to tendus in center, and the ballet class music will be similar to that used at the barre. These are, in fact, essentially the same as the tendus performed at the barre earlier in class but now the dancers no longer have any help balancing.
Just as at the barre, the tendus are once again performed on both sides of the body. While the center tendus are a warmup for the jumps and leaps and large leg movements that will happen during the allegros, performing them in center is also an important exercise in balance and control. Any weaknesses that were present at the barre will be painfully obvious when the tendus are performed without the barre. This is where the tendu can be perfected.
The pianist will use the same musical concepts used in the barre tendus, being aware of the muscle resistance and the tension and relaxation that is inherent in the tendu exercise.
If the instructor chooses to do the tendus slowly, the pianist should fill the spaces with clear phrasing to help the dancer delay the arrival of each new phrase and not rush. This is important so that the dancers get the full benefit of the exercise. A slight elongating of the musical phrase will help the dancer maximize the muscle resistance and delay the relaxation just slightly.
If the teacher demonstrates a fast tendu exercise the pianist can relax and just let loose with a ragtime selection.
For an example of tendu music you can visit Ballet Class Music and hear free samples by composer/pianist/dancer Don Caron from his First Class Album series of ballet class music.