The Classical Seat I, II & III Series DVD by Sylvia Loch A Guide for the Everyday Rider; Advancing the Novice Horse & Rider and Advancing the Elementary Horse & Rider
Starting with the basic knowledge required to sit and to apply the aids correctly, these 3 separate films help the viewer progress ever upward.  In the first section--Classical Seat I-- much attention is paid to the horse's back, his center of gravity and where exactly the rider should sit.  In the section section--Classical Seat II--further work on schoolmasters clearly illustrates the concept of lightness, engagement and rebalance over the hocks.  Finally in the third section _-Classical Seat III--stunning film work confirms the shoulder-in, travers, lateral exercises on the circle, i.e., quarters out, as well as balanced turns on the hocks, Half Pass, Counter Canter and Collection and much more.