Both the Brazilian trio Uakti and the midwestern MASS Ensemble–the acronym stands for Movement and Sonic Sculpture–can claim among their ancestors such shining oddballs as Harry Partch and Leon Theremin (and the couple dozen other instrument inventors compiled on the excellent CD Gravikords, Whirlies & Pyrophones, released by Ellipsis Arts in 1996). MASS builds its physical, engaging performances around the sonic sculptures of Bill Close, a longtime inventor of instruments both practical and unplayable (his local gallery shows have featured impossible guitars and bizarro harps). MASS’s signature pieces are the Close Long Bows, a graceful pair of roughly 25-foot metal frames supporting nine really long strings apiece, though the group also employs such conventional tools as cello, flute, and percussion. Close’s creations dwarf those of Uakti, whose roughly 130 homegrown instruments (it travels with about 40) mostly stick to a more human scale. The group’s name, pronounced “WAH-ke-chee,” comes from an aboriginal Amazonian myth about a creature whose body was full of holes through which the wind blew, creating entrancing sounds. But in seeking different tones and textures, Uakti’s classically trained musicians have traveled far afield from the ceremonial wooden flutes believed for centuries to echo the song of their namesake: at one time they featured a glass marimba, and several of their axes make use of PVC pipes, some of which serve as tuned drums (a technique familiar to Chicago crowds thanks to Stomp and the Blue Man Group). Of these two groups Uakti has the higher profile, thanks to its guest appearance on Paul Simon’s Rhythm of the Saints and a tour with Stewart Copeland a few years back. Its use of Brazilian folk elements–which inspire both its instruments and its compositions–further distinguishes it from the MASS Ensemble, which sounds Celtic when it sounds ethnic at all. Both groups lean on formalism, occasionally to the point of monotony, but on this bill, the music’s only half the draw: when all the players take the stage at once for the concert’s closer, they should make the Star Wars cantina band look like the Juilliard Quartet. Saturday, 7:30 PM, Sidney R. Yates Gallery, Chicago Cultural Center, 78 E. Washington; 312-744-6630. NEIL TESSER

Art accompanying story in printed newspaper (not available in this archive): Uakti photo by Patented Photos.