Progressive dances, such as foxtrot and waltz, are danced on a large dance floor like that in a ballroom or dance hall. Such large floor is divided into two sections: the outer travelling lanes for progressives dancing, and the inner or center floor for spot dancing. Dancing progressive dance needs to follow certain rules, such as travel counterclockwise around the line of dance, do not move against traffic, maintain the flow, avoid spot dancing that could hold up traffic, move to the center if you like to do spot dancing or practice, avoid frequent lane changes, do not travel through the center, keep a proper distance from others (not too close or too far apart), adapt patterns to what the traffic permits, do not focus on completing a pattern if a collision can result, do not force your way to overtake, etc.
Spot dances, such as disco and salsa, are danced in a fixed area. Such dances can be danced on a small floor like that in a restaurant or bar, which tends to be crowded due to its small size. Dancing spot dances on a small and crowded floor follows different rules, such as dancing on your own spot or slot, not drifting around the dance floor, using minimum space, using compact dance hold or embrace, using small steps, avoiding dangerous movements, respecting other's dance space, not pushing or elbowing your way around, etc.
Now, the question is, is tango a progressive dance or a spot dance? What floor size is better suited for tango dancing? Which set of rules apply when it is danced on a crowded floor? There are no simple answers because tango, though a progressive dance in general, can also be danced on a spot. The following is an example.
People do not dance foxtrot and waltz on a coffee table, because that requires a large floor. But tango is different, it is an intimate dance danced in close embrace and compact steps that does not require a huge space. Which is why milongas are often held in restaurants and bars. A small venue is more intimate, readily available, affordable, and easy to do cabeceo. On the down side, a small venue does not hold a lot of people and tends to be congested. In a small bar like the famous El Beso in downtown Buenos Aires, there are often over a hundred people packed in a room about the size of a large American family room, dancing tango. People are jammed together, using whatever space available to them, and dancing in very compact steps, drifting randomly around the floor in a generally counterclockwise direction. Obviously, in places like that you have to follow rules different from that in a spacious ballroom where lanes are divided, free travel is possible, and open embrace and fancy steps are allowed. We dance tango in various venues, some are big, others are small; some are sparsely populated, others are tightly packed. Even a large floor can be crowded from time to time. Therefore, one must dance in accordance with the changing situation. Sticking to the way that no longer fits is a recipe for disaster. For example, dancing in open embrace and using wild steps on a small and crowded floor, trying to finish a pattern even that will result in a collision, or forcing an overtaking that may disturb others' dancing, etc. Such senseless behaviors are a major cause of accidents in our milongas. (See Milonga Codes.)
This happens often because people do not know how to do spot-dancing in tango. Many students are only taught to dance tango progressively in open embrace and fancy steps on a large dance floor. They have never learned to tango on a tiny spot in close embrace and compact steps in a crowded milonga. However, with the growing popularity of tango, the ability to do so is becoming increasingly essential, as our milongas become more and more crowded. Dancing tango on a crowded dance floor requires using close embrace and small steps, such as rock step, ocho cortado, sacada, giro milonguero, the ability to change the body's position from one side of the partner to the other side of the partner in a very compact way, a much better command on dissociation, and the knack in floor crafting, etc. It also requires the dancers to focus more on the music and feelings rather than the steps and performance. Without these skills, one's tango education is insufficient and inadequate.