What are the common economic, organizational, ideological, and aesthetic traits among contemporary genres? Do genres follow patterns in their development? Lena discovers four dominant forms--Avant-garde, Scene-based, Industry-based, and Traditionalist--and two dominant trajectories that describe how American pop music genres develop. Outside the United States there exists a fifth form: the Government-purposed genre, which she examines in the music of China, Serbia, Nigeria, and Chile. Offering a rare analysis of how music communities operate, she looks at the shared obstacles and opportunities creative people face and reveals the ways in which people collaborate around ideas, artworks, individuals, and organizations that support their work.