Now in its 11th year, this spring celebration of the wild world of contemporary music spreads the avant-garde wealth to venues across Manhattan and Brooklyn. Tonight's opening show at Merkin features two ambitious new works by a pair of precocious composers. First up, composer William Zuckerman's newly minted chamber ensemble Symphony Z delves into his expansive 44-minute-long work, Music in Pluralism. Contemporaneous, a youthful collective formed at Bard College, takes over on the second half. The group will perform Dylan Mattingly's Atlas of Somewhere on the Way to Howland Island, penned especially for the group and included on their debut Innova disc, Stream of Stars: Music of Dylan Mattingly (due out April 24).