THE TICKET-TAKERS at the Performance Center, passing around a lot of green paper the other night at the Waylon Jennings concert, were imitating and making fun of the country nasal twang wafting through the door. They piped in folk-rock music between the sets. Inside, in the midst of longhairs, a middle-aged housewife from Ayre rocked back and forth to "Me and Bobby McGee" and a man in his sixties danced to "Six Days on the Road." Cambridge has never been much for country and western music--and this is rare for a college town. But this week, and tonight, the Performance Center--where you pay alot of money for an excellent sound system and not much else--is transformed.

When the bass and drum strike up every one of Waylon Jennings's songs, there's a plodding anticapatory quality about it, a waiting without suspense. This is a familiar theme in country music, connected to country life--the mood is like sitting on the porch in summer whittling and watching the cars go by. It's hard-driving and strong but with a controlled drawl, so that it sounds redundant at first, until the body of the song starts and Jennings and his harp players weave a bluesy exchange through the sameness. Joining them is a superb pedal steel, a rhythm guitar and Jennings on lead. The tunes are written by and large by Billy Joe Shaver--one of the best--and they're basically macho stuff, about outlaws and boozers and a woman associated with every town. But anyone accustomed to country music has gotten over that by now. Waylon Jennings's act is one of the few fine ones left in Nashville, merging country and rock, eluding both labels and seeping a subtle power all its own.

Less professional, less unique and easier to listen to is the band sharing the bill tonight: John Lincoln Wright and the Sour Mash Boys. These musicians are locals and they look it, but at the same time they play more faithful country music than you can hear anywhere, faithful to the Hank Williams and Bob Wills and Merle Haggard and Willie Nelson songs they perform. The only hint of deviation is the inexplicable New England flavor they give to their music, and in a Cambridge environment that's fitting. Vocalist Wright wrote a lot of their numbers, and they're often about Maine and Boston and the like, so that's part of it. But probably the reason that they're right to call themselves a "country and eastern" band is sophistication.

COMPLEXITY AND TECHNICAL ability are the only way you can get away with performing these old tunes, because half the power of a Hank Williams song is mythic: the vision of a train whistle America that's gone; Bob Wills's radio shows in the thirties with chorus girls swaying in cowboy skirts; liquor-riddled voices straining on old records. To make up for this, the simplicity has got to go, replaced by five instruments doing interesting things all at once. Here it's an electric fiddle, pedal steel, lead guitar, bass, banjo, and drums, and they all lend a propensity for jazz-and-rock-like riffs. The Grateful Dead and the New Riders do this with country music, but their songs are different, trippy and abstract rather than sensual and evocative.

The other difference is that John Lincoln Wright has a voice capable of redefining a dead style, like Diana Ross did for Billie Holiday--remaking rather than trying to emulate. He's even versatile enough to pull off country yodeling. Good voices are almost impossible to find in bands that haven't made it yet, as are intelligent ways of mixing, letting each instrument step out and hop over the wall of sound. The Sour Mash Boys have no such problem, which is why they record so well--when their tapes play Saturdays on WHRB, they sound more at home in studio conditions than most of the slick Nashville people who have been playing and selling for years.

The Sour Mash Boys and the Waylors complement each other--the famous part of the bill practiced and calm and in an easy category by itself, the local group sharp with nervous potential and playing straight conventional country. It's amazing that a truly quintessential country and the western band like John Lincoln Wright and the Sour Mash Boys could have risen up in a town where people's idea of a real cowboy bard is James Taylor. But Cambridge isn't entirely unfriendly terrain for a pure and healthy country music to grow in, for these musicians are students in the good sense: If there's one thing students can sometimes do it's imitate with a respect for history. And in this case that's exactly what a corrupted genre needs.