This ancient instrument of northern Australian aborigines is showing up all over the world: in movie soundtracks, the Survivor theme song, rock bands and now, incongruously, in Celtic music festivals.

The low, warbling sound of the "didg," as it's known by fans, is a hallmark of the Australian Celtic rock band Brother, led by siblings Hamish and Angus Richardson. The band integrates both the bagpipes and the didg in their music for ambience.

The Brother brothers and their bandmates, Rick Kurek and Derek Stewart, will be sharing the art of the didg at this year's Greater Philadelphia Scottish and Irish Mid-Winter Festival and Fair. In addition to their three shows, the group is holding a didgeridoo-making and playing workshop after their Sunday show, where you'll learn the basics of the didg.

"The thing about the didg is that some people nail the sound in just a few blows, so that literally within minutes you can be hearing a wonderful, pure sound from the instrument," says Hamish.

The didg is traditionally made from long pieces of eucalyptus wood that have been hollowed out by termites, according to Hamish. But, he says, "many of the didgs that we play in the band are actually ones we've made ourselves from lengths of PVC piping."

Local didg maker Drew Reid will be joining Brother at the workshop. He runs a didg-making business called Didgeridoos by Didgeridrew, and will be selling didgs at the show. Reid happened across Brother in Colorado in 2001, drawn by their bagpipe playing.

"I had just bought a didgeridoo and [Brother] gave me tips," Reid said. "I [now] make didgeridoos for them and they give them away as door prizes and auction them off for a diabetes charity."

If you nail the sound and want to learn more, there is a burgeoning didg community on the Internet, with information ranging from making your own didg to tips on perfecting your style.

Brother plays at the Mid-Winter Festival, Sat., Feb. 15, 4:30 and 9:45 p.m., and Sun., Feb. 16, 1:45 p.m.; Didgeridoo Jam, Sat., Feb. 15, 2:15 p.m.;

Didgeridoo Demonstration, Sun., Feb. 16, 2:45 p.m.; free with festival admission of $18 (free for children under 10), Valley Forge Convention Center, King of Prussia, 610-825-7268.