Having celebrated its 40th anniversary last month, the San Francisco-based Rova Saxophone Quartet has been nestled near the intersection of composition and collective improvisation for decades, challenging the limitations of tradition and blurring the lines between genres. Members Bruce Ackley (soprano), Steve Adams (alto), Larry Ochs (tenor) and Jon Raskin (baritone) draw influences from free jazz, post-bop, avant-rock and blues, as well as contemporary poetry, dance and visual art. Their nonprofit umbrella organization, Rova: Arts, administers the ensemble’s productions, tours and activities and commissions new works by established and emerging composers in order to promote the visibility and growth of the improvised music scene.