A room in a pub. Some musicians facing each other. They play well-known traditional Irish tunes on flutes, tin whistles, and fiddles. Every musician plays the melodic line adding her own variations and grace notes. Some musicians are just listening; others are cracking jokes. The crowd nearby is composed of friends, occasional patrons, a regular audience, and curious tourists. Some seem not to care; some come closer to listen or perhaps even participate. This is called a "session". From an anthropological point of view, sessions are not just a musical environment. They are a combination of...