We schooled a wonderful exercise in our lesson this week in further preparedness for flying changes and (eventually) tempi changes: in (let's say left) canter from the short side turn down the quarter line. Ride the horse completely STRAIGHT, being sure that the horse is aligned between your aids and the haunch is neither in nor out; this exercise lives and breathes on keeping the horse ABSOLUTELY straight in canter; focus on an object on the distant horizon (a tree, fence post, whatever) to facilitate the straightness. Keeping the horse's body straight in a straight left lead canter, do flexions (NOT changes of bend per se, rather changes of flexion) left and flexions right multiple times along the quarter line maintaining the same (left) lead. At the end of the quarter line, turn left along the short side then turn left down the next quarter line and repeat. After a couple of theses straight lines Delphi is very collected, we're both organized, and the flexions are light. Once this amount of harmony is achieved, rather than turning left and coming onto the next successive quarter line, rather turn left at the end of your straight quarter line, ride along the short side wall into the next corner, then come across the long diagonal still in left canter while again maintaining the ABSOLUTE straightness (LOOK UP THE STRAIGHT LINE where you're going). At this stage in Delphi's training, before x, flex right as if you were continuing the straight line exercise, then immediately follow with the aids for flying change. Swish we got several perfect flying changes as polite as can be! You can also ask for the flying change along the quarter line, but ask before the E X B midway line so that you can keep riding straight in the new canter lead, then you must make a volte-type turn in the new direction off the quater line onto the closer wall (to the right in our example). Of course school all exercises in both directions equally. Further along in the training, one could use the same exercise to school the tempi changes along the long diagonal. This seemingly simple exercise REALLY helped me in establishing the straightness and flexions with harmony to prepare for changes that started and stayed balanced and uphill.