In this video I ride Mercurio, a PRE (Pure Rasa Española aka. Andalusian), and describe how to develop the trot from a flat quick trot into a trot that has suspension, elevation, and lift. This becomes a collected trot that is somewhere between a passage and a medium trot. It takes a LONG TIME to develop this trot and for the horse to develop the coordination and strength to carry the trot through the turns and lateral work!
Happy Riding!!