In the recent months, as a result of a few dressage lessons, I have discovered what I would call "elastic contact".
It's a bit like a "push-me-pull-you" game that your horse's mouth plays with your hands. Notice the wording here. It's not "your hands play with your horse's mouth". It's "your horse's mouth plays with your hands". Because that's the truth of it, that while the contact on the reins is initiated by your hands, the game is activated by your horse. More about that in a minute.
It feels like your reins have suddenly got a section of elastic band in them, and they stretch and compress as your horse ambles happily along. You can't use this contact for balancing though - it would be like trying to balance using a rubber band - it will just stretch. But, you can "play" a bit with this contact, driving more horse into it, or stretching it back towards you to slow down.
It feels like the ultimate connection with your horse. Initially it can be fairly heavy handed, like an old rusted spring, but as you get better at it, and your horse trusts you more, it should become lighter and softer.
Have I sold you on the concept yet?
Now, back to initiating this "game" with your horse. Like I said - you, the rider, initiates it by picking up the reins and creating a contact. Your horse then chooses to either brace against you, back off the bit, or to play the game. Naturally, you want the latter.
Dingo braces against you (and generally races off into the sunset). Lilly tends to back off.
The trick with Dingo, is to obtain a contact without allowing him to brace, and then to ask for another 4 millimetres of contact, and then release about 2 millimetres of contact, all the while holding perfect balance with your body, and keeping a really quiet leg. Phew! Yes, not a small achievement.
The trick with Lilly is to send her for a solid fast canter up the hill, with lots of half halts, good or bad, doesn't matter. Then walk back down the hill to the arena, and ask for trot. Presto. Elastic contact every time. Just like magic - as long as you can handle the fast canter.