Four Country Greats on the Road Again as Highwaymen : Collaboration: Johnny Cash, Waylon Jennings, Willie Nelson and Kris Kristofferson team up tonight at the Pacific Amphitheatre.

Country singers are a musically incestuous lot. Every now and then, a couple of pop singers might call time out from their solo careers and team up for a single or two--Paul McCartney and Stevie Wonder for “Ebony and Ivory,” Stevie Nicks and Tom Petty for “Stop Draggin’ My Heart Around,” Kenny Loggins and Steve Perry for “Don’t Fight It”--but it doesn’t happen very often.

Country singers, on the other hand, regularly record entire albums together. Look at the country album charts over the years and you’ll find virtually every possible pairing of heavy hitters: Johnny and Waylon, Waylon and Willie, Willie and Merle, Merle and George, George and Tammy, ad infinitum.

The 1985 “Highwayman” album is one of the most ambitious and successful country collaborations ever, featuring three of the genre’s biggest stars--Johnny Cash, Waylon Jennings and Willie Nelson--and one also-ran, Kris Kristofferson.

The project’s seeds were sown a year earlier, when the four were filming a TV special in Switzerland.

Between shoots, there were several informal jam sessions--and when they returned to the states, they decided to make an album together.

“Highwayman” promptly rocketed to the top of the national country charts--as did the single of the same name--and eventually sold more than 1 million copies.

A few months ago, the quartet resurfaced with a second album, “Highwayman 2.” And they’re currently in the midst of what a press release maintains is their “final tour as a foursome”--a 23-city, cross-country sweep that includes an appearance tonight at the Pacific Amphitheatre in Costa Mesa.

Even though each member of the band has done quite well on his own, the Highwaymen, as the four-way partnership has come to be called, is a perfect example of the whole being even greater than the sum of its parts.

Nelson’s starry-eyed romanticism and nasal whine are countered by Jennings’ robust machismo and gruff bark; Cash’s penchant for dramatic overkill is countered by Kristofferson’s weary subtlety. And vice versa.

They keep each other in check--and the result is something of a musical checkmate.

The first album is by far the superior one. Standouts include the title track, a classic I’m-gone-but-not-forgotten tune written by Jimmy Webb; a gripping rendition of Woody Guthrie’s heart-rending “Deportee (Plane Wreck at Los Gatos)”; and an intense remake of Cash’s own “Big River.”

The second album is good but not great. “American Remains” is essentially a rehash of “Highwayman,” and Nelson’s “Texas” is a pretentious tribute to his home state. But “Silver Stallion,” written by Lee Clayton, a longtime member of Nashville’s “underground,” is a wonderful Western ballad of the kind Gene Autry and his fellow “singing cowboys” used to sing on the silver screen, and “Born and Raised in Black and White” finds the foursome doing some splendid choral singing.

Waylon Jennings, Willie Nelson, Kris Kristofferson and Johnny Cash play tonight at 7:30 at the Pacific Amphitheatre, 100 Fair Drive, Costa Mesa. Tickets: $22 to $31.50. Information: (714) 634-1300.