Throat singing, a technique where two or more notes are sung simultaneously, can create sounds ranging from guttural didgeridoo-like rumblings to unearthly shrieks. Alash, a trio from Tuva in southern Siberia, are musical ambassadors for the centuries-old form, touring extensively in America and collaborating with artists like Bela Feck. Alash tweak traditions by blending western instruments, harmonies and song structures into their hive of swarming voices. But their remarkable mouth music retains its alien beauty and mystery.