Rolling on like the big wheel he frequently sings of, Joe Turner still sings the blues with booming power and rich rhythmic variety 40 years after he first took part in the free-wheeling jam session atmosphere of Kansas City in the '30s.

Turner, who opened Tuesday at the Showboat Lounge for a six-night engagement, sang the other night with much of the jauntiness and subtle coloration that has long characterized his work.

He skipped through "Yakety Yak," hitting low notes with the ease of a young singer. And he still has a marvelous way of repeating the same phrase (in this case, "Hi-yo Silver!") with ever-changing tonality, melody and enunciation.

Always a huge man, Turner is so large now that he sings sitting down and walks ith a cane. When asked about his weight, the 6-foot-1 1/2 singer snapped, "That's personal. I used to be skinny. People called me 'TV Joe.'"

He blamed his weight (350 pounds would not be an exaggerated guess) on eating rich food ("lots of French bread and butter and cream" in New York in the '50s). Yesterday he was drinking boilermakers (scotch and beer) despite his diabetic condition.

musically, Turner has been one of those rare artists whose music has directly touched several generations - and audiences.In the '30s, his following was a Midwestern jazz group. BY the '40s, he'd moved on to New York and built up a primarily white audience.

Still, the '50s brought his most fame - among young Southern and Western blacks and young big-city whites. He recorded "Shake, Rattle and Roll" before Bill Haley and the Comets, and followed it with "TV Momma" and "Chains of Love," winning the hearts of the first rock 'n' roll generation.

Turner says he works about six months a year. The other six month's he spends at home in Los Angeles.

Before opening Tuesday night, he had appeared for a one-nighter in Providence, R.I. Though delivering a spirited performance the other night, he didn't really go all out, probably because the Showboat was practically empty. About 10 persons showed up.

"You got to expect this after a holiday," chuckled Turner. "Everybody gets kind of raggedy after a holiday. I'm glad it ain't Christmas."