POP MUSIC REVIEW : Harris’ Pleasant Surprise : The country singer, with the Nash Ramblers at the Crazy Horse, puts a fresh spin on some of her oldest tunes instead of focusing on her latest album.

If the Greek philosopher Heraclitus had been an Emmylou Harris fan, his proverb “you can’t step into the same river twice” might have come out “you can’t attend the same Emmylou Harris concert twice.”

Harris’ 17-year-career has been marked by more unexpected turns than an Agatha Christie thriller. Her 1-hour, 15-minute early show at the Crazy Horse on Monday night may not have been as surprising as her last Orange County gig--when she astounded local concert-goers by showing up with an all-acoustic band instead of her longtime electric country rock group, the legendary Hot Band. Still, unpredictable is the only way to describe it.

Because she had not played in Orange County since her current album, “At the Ryman,” was released, one might think that Harris would have built her set around material from the album. Instead, she used her acoustic band--the Nash Ramblers, still with her--to give a fresh sound to some of her oldest tunes.

The 16-song set included only three from “At the Ryman” and only one other ‘90s vintage number, “Ramblin’ and Gamblin’ (The Death of Hank Williams)” from her 1990 album “Brand New Dance.” Every other song on the program was at least a decade old.

The acoustic setting made even such chestnuts as “Wheels,” “Sweet Dreams” and “Ooh Las Vegas” from Harris’ second album, “Elite Hotel” (1975), sound practically new. For example, during “Ooh Las Vegas,” the hot electric guitar solo that used to be the tune’s centerpiece was replaced by dazzling mandolin picking by Sam Bush.

Similarly, instead of Hot Band guitarist Frank Reckard’s stinging licks on “Born to Run” from Harris’ album “Cimarron” (1981), Nash Rambler Al Perkins supplied the juice with some stunning country rock dobro.

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Even though Harris only played three songs from “At the Ryman,” she managed to tap the intriguing eclecticism of the album. With brilliant vocal harmonies from the Ramblers, she sang Stephen Foster’s 19th-Century standard “Hard Times,” following it with the quintessential cowboy yodel song (Harris couldn’t quite manage the yodel) “Cattle Call,” which she dedicated to singing cowgirl Patsy Montana. Finally, Harris and the Ramblers pulled out all the stops for a searing rendition of Bill Monroe and Peter Rowan’s modern bluegrass tune, “Wall of Time.”

It may seem hard to believe that Harris ever could find a touring group that could surpass the Hot Band (whose alumni include such Nashville hotshots as Ricky Skaggs, Rodney Crowell and guitarist Albert Lee, currently with the Everly Brothers), but the way the Ramblers have settled into her repertoire suggests that they may become her greatest band ever.

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Leader Bush was responsible for the most spectacular instrumental fireworks of the evening with his mandolin and fiddle. Perkins not only spiced up numbers with his dobro but also supplied some driving banjo. Guitarist Jon Randell Stewart sang a lovely duet with Harris, “Hello Stranger,” and contributed a hot acoustic solo to “Walls of Time.”

Drummer Larry Atamanuik and bassist Mark W. Winchester, who recently replaced original Ramblers bassist Roy Huskey Jr., were an appropriately low-key rhythm section. Atamanuik, in particular, was wonderfully sensitive. His full drum kit easily could have overwhelmed the acoustic instruments, but never even begun to.