Jazz musicians have often gone on record decrying the use of "labels" by writers and critics, and from its beginnings the terminology has lent itself to confusion. The very word "jazz" was an amendation of "jass" for reasons as obscure as the origins of the word itself. (Original Dixieland Jass Band leader Nick La Rocca claimed that pranksters kept removing the "j" from marquees.) Today the term is exchewed by some who favor nomenclature such as "Black American Music and Its Extensions," "Great Black Music," or simply "creative music."

Then there is "swing" -- a noun and verb denoting, respectively, a style and an indefinable quality without which the music does not . . . well, swing. "Traditional," once used solely to indicate the early New Orleans sound, its subsequent developments in Chicago in the 1920s and its later recreations, is now applied to New York style "Nicksieland," big band and even bop. As for "cool," "free," "The New Thing," and "fusion," they too have suffered a diminution in exactitude.

"Mainstream," coined by jazz historian Stanley Dance in the '50s, originally encompassed the body of musicians who came up in the "Swing Era" before the advent of "Modern Jazz." But these days one finds lumped together under that rubric everyone after King Oliver and before Ornette Coleman.

The following recent albums have been selected in an attempt to redefine the term by example and restore to it its pristine connotation.

"A Perfect Match" (Pablo Today D2312 110/Digital) is truly that -- between Ella Fitzgerald and the Basie band. She romps through "After You've Gone" and Sweet Georgia Brown," scats "Honeysuckle Rose," gets down on the "St. Louis Blues," and serves up several lush ballads including "You've Changed." The authoritative West Coaster Paul Smith (lately Ella's accompanist) sits in for the Count. Washington's own Keter Betts (who travels with the vocalist) plucks his big bass and trombonist Bootie Wood and Ella get a conversation goin on "Basella" in which voice and horn are often indistinguishable. The Count resumes his throne for a corker of an instrumental album (Pablo Today D2312112/Digital), cut on the same day. Both efforts were "live" to an enthusiastic audience in Montreux, Switzerland.

The earthiness, robustness, and vicacity of the great ex-Basieite Helen Humes are captured in a session that dates from 1973, soon after she had made her comback. "Let The Good Times Roll" (Classic Jazz 120) has assorted back-up personnel: Jay McShann and the late Milt Buckner at keyboards, Al Casey on guitar, Arnett Cobb and Candy Johnson on tenors. "My Handy Man" and "They Raided the Joint" are standouts.

Rick's Cafe Americain in Chicago is the scene of two on-location recordings that belie the notion that the "mainstream" has dried up. Trombonist Al Grey and tenorist Jimmy Forrest team up with pianist Shirley Scott, bassist John Duke, and Bobby Durham at the drums on "Live at Rick's" (Aviva 6002). The quintet blasts its way through Bird's "The Jumpin' Blues" and delivers a bouncing "In a Mellowtone." Grey's growling "Summertime" is a torrid tour de force that brings to mind the classic version recorded in 1939 by soprano saxophonist Sidney Bechet.

The similarly titled "Live at Rick's Cafe Americain" (Flying Fish 079) brings together a remarkable group of mainstreamers: Red Norvo is at the vibes, Buddy Tate on tenor, Urbie Green on trombone, Dave McKenna at the piano, and Barrett Deems on drums. All have roots in the '30s and '40s and wide experience in large orchestras and small combos. The younger Steve La Spina is on bass. A nearly 11-minute jam on Charlie Shavers' "Undecided" lets everyone stretch out and it is a steamer. The medley of "I Can't Get Started" and "Everything Happens To Me" showcases Green on the first and Tate on the latter. Deems' traps push "Green Dolphin Street" to an all-hands-on-deck rideout. McKenna and Norvo take over on a sensitively rendered "Here's That Rainy Day."

The Scott Hamilton-Warren Vache "Skyscrapers" (Concord 111) attains a big-band sound, and not surprisingly -- their group is about the size (nine pieces) of the early "big bands" of Ellington, Jelly Roll Morton and others. For this studio session the breathy and big-toned tenorist Hamilton has augmented his fine quintet with Peer Vache on cornet, oldsters Harold Ashby on tenor and baritonist Joe Temperley, and the brash and gutty trombone of George Masso. It is a splendid gathering of mainstream stalwarts, notwithstanding that two-thirds of the participants are still in their twenties.