Name-checked by countless musicians wise to the avant-garde (and demonized by hordes irked over his misrepresented comments casting 9/11 as a "work of art"), Karlheinz Stockhausen is a complicated figure. Musically, his legacy rests most strongly on his experimental electronic music from the '60s, but his composition also settled into more traditional settings. Here, Elisabeth Klein plays a series of works for solo piano, an instrument that sounds both foreign and familiar in Stockhausen's heady scores. "Tierkreis" follows a moody meditation over heavy and light clusters of notes, recorded raw to let tinkling turn to tatters. "Klavierstuck IX" takes the portentous mood straight to a catastrophic end; its opening key crash sounds more and more powerful as its reappears through ten ominous minutes. The bulk of Stockhausen's pieces are dark and discordant, but it's a kind of discord that wonders aloud about its own power. Pieces like "Aus den Sieben Tagen" focus on gnarled tangles of chords, but they also drift through swooning trills of classical beauty, making much of mood shifts and short spells of silence reconfigured as something more suggestive. It's the kind of classical music that favors both jolts and lulls, guarded against ears uninspired by surprise.