EVERY OTHER pop band of the moment is jumping on the time-machine bandwagon, spinning back in time for influences and ideas and fashion sense -- some going back as far as 1967.

Dead Can Dance does the time warp, too, but this contemporary British outfit isn't satisfied with skipping back a mere decade or two. Dead Can Dance hurtle backward through eons. Their "new music" sounds ancient, set apart from the pop rabble by the archaic instrumentation -- the sound of tolling bells, skirling bagpipes, Celtic harps and droning hurdy-gurdy -- and songs sung in long-forgotten tongues.

This uncategorizable band -- actually just a core of two, singer/songwriter/producers Brendan Perry and Lisa Gerrard, plus occasional hired musicians -- dig back (think archaeology) as far as the 14th century for inspiration.

The duo, which appears Friday at Georgetown University's Gaston Hall, is forever being compared with Cocteau Twins, with whom they share a record label (4AD), a taste for gorgeously ambiguous album graphics and titles, phantasmic singing and often indecipherable lyrics. They have in fact performed with the Twins on an occasional project under the name This Mortal Coil. But the Dead Can Dance mission is quite distinct, and unlike the clamlike Cocteaus, Perry at least is quite happy to talk about what he does and what it might mean.

The Anglo-Irish couple, "soul twins," as Perry calls them, were introduced by a drummer friend in Melbourne, Australia in 1980. Perry had already formed his group, and invited Gerrard to join as an instrumentalist, soon discovering that Gerrard was a gifted songwriter and blessed with a bewitching voice of uncanny beauty and range. Perry himself has a gravely serene baritone, and when the voices are entwined the effect is both sepulchral and ecstatic.

The duo's last album, "The Serpent's Egg," sounded like the hymnbook of some arcane cult that meets in catacombs -- night music to be listened to clandestinely, by candlelight. The latest, "Aion," continues the forbidden feel, and its eerie grandeur derives from farflung sources, from the Middle Ages to the Middle East, sometimes evoking solemnly liturgical dirges, sometimes conjuring images of dancing dervishes or perhaps Salome shedding a veil.

None of Dead Can Dance's five recordings are available domestically in the United States, meaning American fans must seek out import copies and shell out nearly double for the privilege.

This group has just begun its first U.S. tour, and last week the seven-piece incarnation of Dead Can Dance made its stateside debut in Boston, where Perry says they were called back for three encores.

"I don't know whether that's obligatory here or what," he says, and laughs. "We played for two hours, and about 70 or 80 percent of the set was completely new material. We're not playing any of the old ones. I think they were shocked."

Not that Dead Can Dance has anything you might call "hits," in any sense of the word. But oddly, with no airplay to speak of -- who would play it, what radio format would it fit? -- "Aion" (Perry pronounces it "Eye-on") is selling rather briskly. A spokesman for 4AD reports that it imported 10,000 copies for U.S. distribution. Now, that's nothing next to a Madonna, of course. Or even Cocteau Twins, who have domestic distribution here. But this is a group that shrugs at, if not shuns, success.

"We really don't have to do anything to survive in the Western world, what with welfare and social security programs," Perry says. "So we're not in a way tempted by commercialism."

Like fellow ethnopirates Paul Simon, Peter Gabriel and Sting, Dead Can Dance plunder other musical worlds, and sound quite expert in their exotic instruments and foreign tongues. But Dead Can Dance don't consider themselves "musicologists" in any formal sense, though Perry says he and Gerrard are aware of formal structures, and their travels often bring them lyrics, poems, melodies and exotic instruments.

Where most contemporary pop groups base their riffs on the rhythms of Africa and Latin cultures, Dead Can Dance go farther afield, chosing music from other continents and cultures. If Dead Can Dance ever felt compelled to come up with a dance track, it would more likely be set to a tarantella than a house beat.

"On this tour, we're doing a few interpretations of early troubador/trouv`ere music, also some medieval dances which we've done arrangements for, but apart from that it's all original material," Perry says. "I think the visual element of our performance is really the strange instrumentation. We've brought along a Celtic harp; a hurdy-gurdy; various guitars, including a Turkish guitar and a Renaissance mandora, which is like a bass mandolin; various wind instruments; African, Oriental, and Eastern percussions; Chinese dulcimers . . . ."

Perry says the group plays these exotic instruments purely by ear. "We've had no academic training whatever."

About the band's faintly forbidding name. Perry says he intended to describe the act of creation itself.

"Animacy from inanimacy, life from death, which seems to be the one great creative aspect attached to all human communications," Perry says, "the way you can give life to things that were not living. The same way you take a wooden instrument, and through your interaction creating resonance, bring it to life. It can be just a simple tune or profound meaning or whatever. It's the wonder of that that still excites me."

DEAD CAN DANCE -- Appearing Friday at Georgetown University's Gaston Hall. Call 800/543-3041.