Call it the Stockhausen conundrum: even as modernist and avant-garde works alienate mainstream classical audiences, they intrigue fans of the noisier subcultures of so-called popular music. Here in New York you can often hear some very severe twentieth-century fare in dusky, clubby spaces. One is Galapagos, in Williamsburg, which, I learned through Eppy, is presenting a new-music series entitled Darmstadt. On Wednesday, Emily Manzo plays a free concert of John Cage, Galina Ustvolskaya, Eve Beglarian, Mary Halvorson, and Chopin (!), with video projections by Andy Graydon. Meanwhile, on Tuesday night at 8PM and 10PM, The Stone, John Zorn's new club, presents the Dedalus Quartet in back-to-back concerts of Elliott Carter, Kurtág, Feldman, Nancarrow, and György Ligeti. And, on Thursday, Lukas Ligeti, the great man's son, does a solo show in the same space.