Modern western square dance dance, like traditional square dance, is directed by a "caller". In modern western square dance the caller strings together a sequence of individual "square dance calls" to make a figure or sequence. These calls are the building blocks of the choreography that is danced by the individuals – square dancers – in the squares. There are eight people (four pairs of males and females, traditionally) in each square; at a dance there may be many squares. Generally speaking, each of these squares dances independently of each other, with the exception of specialty or "gimmick" dances, where there might be some
Challenge square dance partially filled by real dancers. Challenge dancers must learn to do their part of a call in a particular formation even though many of the other dancers – possibly all of them – are missing. This requires both a clear understanding of the call definition and the ability to remember where the positions of the formation are without the usual visual and tactile cues. Calls which cause the dancers to change from one formation to another ("shape-changers") are especially challenging to dance with phantoms because the positions themselves will be changing and the entire formation may have to move to