Mus is a card game with Basque roots that is played mainly in France and Spain, as well as Germany. It is played by 4 players in 2 teams. The team partners. Combining aspects of poker with the strategy of chess, team play with multiple rounds using the signs to partners as well. This Basque card game is a lot of fun. Popular card game in Spain for 2 pairs which basically consists of betting in different kinds of bids. Online Mus. Register to play.