How do I develop correct headset and frame for western pleasure without creating tension?

Headset in western pleasure is a topic that generates significant discussion and some controversy, because the history of the discipline includes periods where extremely low, behind-the-vertical head positions were rewarded and periods where more natural, correct carriage was emphasized. The current judging standard in most organizations rewards a head position that is natural for the horse's conformation and level of training — poll at or slightly above the level of the withers, face at or slightly in front of the vertical, jaw relaxed — rather than either an artificially elevated position or an excessively low one. The critical principle in developing headset is that the head position is a result of correct training rather than a goal in itself. A horse that has been developed through the back — with engaging hind legs that drive energy forward, a swinging back that lifts and carries the rider, and a topline that is soft and through — will naturally carry its head in the correct position as a consequence of that development. A horse that has been forced into a head position through draw reins, tie-downs, or sustained rein pressure without the foundational body development to support it will show that forced position through tension in the jaw, restriction in the neck, and a disconnected, choppy quality of movement. Building the frame correctly begins with lateral flexion and vertical yielding exercises that teach the horse to soften through its poll and jaw in response to light rein contact. These exercises should be done at a standstill and at the walk before they are attempted at the jog or lope, because softness is easier to establish at slower speeds and the habit carries forward to faster gaits once it is confirmed. A horse that is soft, round through its topline, and carrying its head correctly will maintain that frame with minimal rein contact during the class. A horse that requires constant rein management to hold its head position has not been developed correctly and will show that requirement as tension and unevenness throughout the class.