A simple definition. ‘When either foot is moved across the body, whether in front or behind, the body is said to be in Contrary Body Movement Position (CBMP)'. I've coached beginners and championship dancers for the past 48 years and in that time I've heard a considerable amount of controversy upon the position known as, CBMP. Even today, some assert that whenever one foot is placed across the body, irrespective of whether there is any turning movement or not, CBMP is attained; others claim that CBMP can take place only when there is no rotary movement whatsoever. A past coach and dear friend of mine discussed this position with an anatomist and a professor of dynamics and satisfied himself that the former school of thought is theoretically the correct one. Actually, therefore, if the claim of some of the UK coaches that the axis foot in turning movements should be placed slightly across the front of the body is a legitimate one ( and the writer is convinced it is) then slight CBMP should always occur simultaneously with Contrary Body Movement (CBM).

I agree.

To go further, the older definitions of CBMP (and the name itself) suggest that this is a position like that achieved from full CBM, but occuring in isolation from a rotational cause. Usually this is because it is a carryover from rotation on a previous step.

We can actually make this precise enough to apply to tango as well. CBMP is the result of the direction in which the body is aimed by the time one leaves a stable position over the standing foot. CBM is any (suitable direction) rotation occuring during the course of the step. In tango unlike the swing dances, the lack of body flight means we can rotate our course in place over the standing foot before taking a step, and the result of this could be CBMP. In contrast, if we rotate during the step we are using CBM.

To further illustrate the difference, consider an outside partner waltz natural. Step one is to be placed in CBMP because the body momentum has already been aimed outside partner during the previous figure. No matter what figure we might choose to substitute, it is preordained that step 1 must land in CBMP. But CBM is a matter of choice - during the step into the predesitined position, we have the option of introducing an addition rotation of the body over the feet, in order to create a turn over the following steps. Here CBMP and CBM are co-occuring, but can still be analyzed in isolation - the CBMP is in no way due to the coincident usage of CBM.