From her first steps, the tango follower faces the doom of spending most of her time with only one foot really connected to the ground. She learns "The Basic": side step to her right (onto her right foot); walk back (left foot), walk back (right foot), cross (left foot, though now it's on her right), walk back again (right foot), side step (left foot). She first shuffles from one point to the next as in a children's game: Simon says step right. Simon says step back. Cross your feet. (You're out!) After forgetting which foot she's supposed to be stepping with a few times, getting her toenail polish removed the hard way as the leader descends onto the spot the follower's "free" foot was supposed to have vacated, she learns to hold her free foot up away from the floor flamingo-style while waiting for the leader to decide her next injury. After a year or two of nagging from her instructors, she manages to reconcile her estranged feet, pressing her free foot sideways against the one holding her weight without actually settling into it or forgetting which is which. But she still must effectively commit to one foot or the other most of the time, leading to her obsession with balance: for standing on one foot without falling over naturally implies having good balance, no?
But dancing tango revolves around standing on one foot about as much as solving calculus integrals revolves around remembering your grade school multiplication tables. In either case, the latter might (or might not) be a useful step somewhere along the learning path, but getting stuck there is certainly to miss the whole point. The ability of Utah's Balanced Rock to hold its precarious perch for millenia does not make it an exemplary dancer. Dancing is about moving, not standing; gracefulness comes from dynamic rather than static stability. The goal is not to have perfect balance, but to lose it in the perfect way, over and over.
The average follower clings to her points of static stability like Balanced Rock. After taking one step, she tries to stay balanced on the foot she landed on - seeking that infinitesimally small body position at which she could in theory balance on that foot forever without my help - until she figures out where her next step is supposed to be. If the last step didn't land her in a perfectly balanced position, or if I continue moving a little bit after she has planted her free foot and thus committed to a particular balance point, or if for whatever reason our mutual weight shifts slightly in one direction or another after she has taken the step but before I have given her a clear lead for the next step, then she compensates by contorting her body, or by suddenly hanging from or pushing against me, in order to return to that position at which her inner ear tells her she belongs. We can dance this way, more or less, but we fall far short of having real connection.
The exceptional follower with whom I find dancing a true delight, in contrast, knows that the position of her weight is my problem; her only job is to keep her body connected with mine. If I push her or allow her to fall slightly off-center, she does not know or care whether it represents the beginning of a step, a parada (stop or check-step), a volcada (lean), or just a mistake on my part or hers. She trusts me, allows her body to shift off-center where I place it, and continues pushing into the floor with her anchored foot. Since she is off-center, the force vector of her weight pushing into the floor now has a horizontal component, and old Newton pushes back, accelerating her horizontally further away from that center. Her anchored leg is no longer directly vertical, but is now the hypotenuse of a right triangle represented by her hips, her anchored foot, and the point at which her weight projects onto the floor. To keep her motion truly horizontal with mine and avoid falling toward the floor, she pays Pythagoras his due by gradually extending her initially-bent standing leg as she pushes into the floor with it.
If I allow our bodies' motion to continue, I am implicitly or explicitly - it matters not which - inviting her to fall horizontally with me. As she falls further off-center, she must push harder into the floor to keep her motion horizontal, and must stretch her anchored leg further and more quickly to compensate for the further extension of her leg's hypotenuse. Pushing smoothly outward off the floor this way demands both active muscle power and careful control, and she builds the athletic strength to do this on every step only after returning home from many practicas and milongas with thighs out-aching even her feet. But her reward is that each horizontal fall accelerates away from her old center toward a new one as if putting her in flight, liquidly transforming what starts as a barely perceptible imbalance into a powerful, deliberate tango step matching the whhhhhhUMP of a Pugliese beat.
At the closing UMP of the beat, she eventually runs out of leg to stretch, and unable to prolong her horizontal flight anymore, she must finally submit to gravity and land on her free foot. Where has this free foot been during her flight? She has been holding it almost directly underneath her, like landing gear, at all times tracing the point on the ground at which she would fall softly and silently into perfect balance if her flight happened to end at that point in time. For she never really knows, in fact, where her flight will end until it does: I could stop it anywhere - at a half beat, a full beat, two beats... I might not end it at all, but instead catch her in mid-flight and push her back toward her original center for a volcada.
The beginner's natural habit of timidly extending her free leg in the direction of her step before committing real weight to it - especially common when the direction is directly forward into my space - effectively ends her flight before it has begun. For fear of losing balance or stumbling along the way, she never takes flight at all but only shuffles from one static point to the next. The experienced follower in contrast relishes the feeling of pushing the full weight of her body with mine out into the unknown, away from her point of static balance in any direction whatsoever, with or without accompanying rotation, trusting in my lead and in her own ability to find the floor (where else?) directly beneath her if and when she eventually needs it. She does not try to stay "on balance", but to the contrary wants to spend as much time as possible off balance, because it is the off-balance times that create the gliding, pulsing feeling of tango motion.
And what of me, the leader? The only way I can gracefully lead a woman into a flying horizontal fall is by first pushing my own body into the same horizontal fall. If I want her to go, I must go there with her - with my body, not with my free leg - trusting that I will somehow find the floor once we arrive at wherever I decide we should arrive. If I merely steer her with my arms or push her in the desired direction by contorting my upper body, I am behaving not as a leader but a back-seat driver: an armchair general trying to direct my courageous, curvaceous foot-soldier from the safe headquarters of my static balance point, acting as nothing more than a pushy Balanced Rock. A beginning follower who doesn't know better may put up with my distant generalship for a while, but will quickly desert me for a true leader as soon as one appears.