"JAMMING" is as old as jazz itself and, in some cases, synonymous. The term describes the act of improvisation but also refers to what happens when a group of musicians who don't usually perform as a unit get together for some informal, strictly-for-fun playing.

Ironically, some of these fun jam sessions produce extraordinary results and jazz folklore is filled with stories about Charlie parker burning up some after-hours club with a pickup band and Art Tatum stunning early-morning crowds with impromptu sets. Some of this music is documented through recordings but much of it never remained after the act since jams are, by nature, spontaneous. You still never know when a group of first-class players will wind up in the same place an decide to cook.

Unless you're Norman Granz Tablo Records czar Norman Granz know because Norman Granz sets the time and the place and the players. And if you're thingking that all this prearrangement takes the freshness out of the product, you need only listen to "Montreux '77: The Art of the Jam Session" (Pablo Live, 2620-106) to be convinced that the art lies in the talents of the musicians and not in the enviroment.

For this eight-record boxed set (all the music is available on six individual records, give or take a side or two), Granz brought his stable of players to this year's Montreux (Switzerland) Jazz Festival and put them in front of live audiences and in the studio. In three days he had some great music by the great masters etched irrevocably in vinyl.

Improvisation traditionally revolves around the melody line of a familiar piece. Unlike the "loft" or "new music" practitioners, who do not use a well-known foundation as a base for experiments, the Pablo musicians are from the old school and rely on popular tune or original compositions as Starting blocks.

The package thus include standards like "Sweet Georgia Brown," "Just in Time," "Mack the Knife," "Mean to Me," "Pennies From Heaven," and "She's Funny That Way," all of which serve as launching pads for Oscar peterson, Dizzy Gillespie, Milt Jackson, Joe pass, Zoot Sims, and ageless wonders Count Basie and Roy Eldridge.

If you like you jams self-written, there are Jackson's "C.M.J.," Ray Brown's "Slippery," Gillespie's "Here 'Tis" and "The Champ," Base's "Trio Blues" and "Jumpin' at Woolside," and a slew of collaborative efforts.

Granz seems obsessed with recording everything these artists do, thus (he feels) preserving their place in America's artistic consciousness. So the jams presented here are engineered to show off everyones abilities in nearly equal doses. Most of the tunes are structured to quickly establish the melody line, promptly enabling each musician his allotted solo.

This technique gets a bit predictable over eight records but the solos themselves never do and and, the ensembles' personnel changes, coupled with the combination of a live audience and the emotional flow of old friends reunited, bring out the best in everyone.

Milt Jackson is especially lucid, getting clearer and quicker with age. Oscar Peterson (who now shows up with so many people on so many record labels that he may wel be the most recorded jazz artist of the past five years) turns in some fine work, especially on his own "Ali and Frazier." Gillespie and Basie also sound far more inspired in their jams than they have on recent studio releases.

There are exceptional moments from Clark Terry, Monty Alexander; Jon Faddis, Ray Bryant, Benny Carter, Vic Dickenson, and Al Grey, and some magnificent soloing by Danish bassist Niels Pederson in support of Petersen in support of Peterson on "You Look Good to Me" and "Reunion Blues."

Six separate sets (all titled "Montreux '77" and all Pablo catalog numbered 2308) make up the eight albums presented: "The Oscar Peterson Jam" (pablo Live 208); "The Milt Jackson/Ray Brown Jam" (Pablo Live 205); "The Pablo All-Stars Jam" (Pablo Live 210; "The Dizzy Gillespie Jam" (Pablo Live 211); "The Count Basie Jam" (Pablo Live 209); and the studio session, "Oscar Peterson and the Bassists" (Pablo Live 213). Since all these albums are single copies, some music contained in the full-sized "The Art of the jam Session" is necessarily omitted. A full side of the Peterson jam and two tracks from the Milt Jackson/Ray Brown date are missing from those specific records and there are one or two other variations among the other.

Still, as individual albums or in orne large package. "The Art of the Jam Session" is hours of good listening and proof that to jam is literally to create music. And creativity translted into formis what art is all about.