Over the last decade or so, regular tours by ensembles like Huun-Huur-Tu have blunted the novelty of khoomei, the throat-singing tradition native to the remote, mostly rural republic of Tuva, between Mongolia and Siberia--but the otherworldly beauty of its polyphonic chants and melodies remains undiminished. Chirgilchin is a quartet of young musicians--all still in their 20s--assembled in 1996 by Alexander Bapa, a percussionist and producer for Huun-Huur-Tu who sometimes plays with the group; on both its fine albums, Chirgilchin brings a windswept charm and folksy elegance to strictly traditional material. But the strong presence of a female vocalist, Aidysmaa Kandan, proves the group isn't old-fashioned, its ancient repertoire notwithstanding: the taboo against women practicing khoomei (it was believed to cause infertility) is only slowly receding, despite notable exceptions like experimental singer Sainkho Namtchylak. The group performs its songs on native instruments like the igil, a two-stringed spike fiddle, and the khomuz, a sublimely flexible mouth harp, the jaunty rhythms consistently echoing the sound of a cantering horse (herding sheep and goats on horseback is still a big part of Tuva's economy). But it's the throat singing, sometimes called overtone singing, that takes center stage. Performers manipulate the mouth, throat, and vocal cords to filter out most of the overlapping tones that make up the normal human singing voice; what's left is a handful of distinct harmonics, which can sometimes be controlled independently--early Western observers often described throat singers as having "two voices." The five principal Tuvan styles range from sygyt, a humming drone paired with a teakettle whistle, to kargyraa, a floor-rumbling, Howlin' Wolf-like roar layered with overtones. This free concert is Chirgilchin's Chicago debut. Wednesday, March 21, 7 PM, Preston Bradley Hall, Chicago Cultural Center, 78 E. Washington; 312-744-6169.