LAWRENCE WHEATLEY'S Homemade Jam is appropriately pre-cooked.

When 10 of Washington's top jazz musicians come together in concert Thursday at the First Congregational Church (10th and G streets NW, near Metro Center), they will be celebrating not only Wheatley's original compositions, but his ongoing contributions to Washington's jazz spirit.

For the past three years, the pianist has been leading the Sunday afternoon jams at One Step Down, sessions that have attracted established and aspiring musicians. Before then, he led jam sessions at Columbia Station; as far back as 1967, he was involved with jams at the old Jazzland at 14th and Girard. "I just found a photo taken in 1954 at a jam session in Heidelberg where I was in the 7th Army Special Services," Wheatley says, to certify, unnecessarily, his ongoing commitment to jazz.

Wheatley, who is something of a legend in Washington's jazz community, has always been a Thelonious Monk kind of figure. It's not that he's consciously reclusive, but he seems to choose his public moments with caution. "One of the things I've always tried to do is establish fairly sound criteria and adhere to them," Wheatley says. "When I look around at other piano players, I see what they're doing and try to think of something else to do."

Although Wheatley is a full-time musician, he's more likely to be teaching, composing, arranging or coordinating jams than struggling with low-paying gigs in neighborhood clubs; all that has helped develop his reputation as a recluse, which he laughingly refers to as "the difference between hip and hype."

Wheatley started piano lessons in the third grade. He grew up listening to distinctive vocal stylists (Billie Holiday, Nat King Cole, Dinah Washington) and innovative bandleaders (Duke Ellington, Jimmy Lunceford, Count Basie). The sphere of influences has expanded with the times. "My most recent score, 'Chuckles,' reminded me of Ornette Coleman, in a funny way," Wheatley says. "He wrote a 12-bar blues called 'The Turnaround' and without really being conscious of it, I wrote a variation on a blues that rhythmically approaches, but harmonically and melodically, is a turnaround on it."

Besides Wheatley, Thursday's concert will feature many of Washington's finest jazz players: Commodore Charlie Young on baritone sax; veteran Buck Hill and young Ron Holloway on tenors; altoist Roger Woods, recently named by downbeat magazine as the most promising student soloist in the country; ex-Basie trombonist Lincoln Ross; Vic Stein and Keith Holmes on trumpet; Dave Jernigan on bass, and Wynard Harper on drums.

"Homemade Jam," which is both a group concept and a series of pieces, had its genesis in Adams-Morgan ten years ago, according to Wheatley. "There was a piano shop over on 18th Street, near Millie and Al's, and on Thursday evenings at seven we used to meet there in jam sessions. Every week, I'd bring in one or two pieces arranged for a group. I had been doing a little writing before that, mostly because people had pushed me to teach. I felt since they approached me, they must be interested in what I'm doing, so I started putting it down for illustration." Wheatley adds that the inspiration for writing for a large group came from walking by one of those early 18th Street jams, looking in the window and seeing "all those horns. I said. 'Well, they could use some organization,' and I started scoring charts."

Wheatley has performed with all of the Homemade Jam players in various guises, adding that Buck Hill, with whom he played for a couple of years at Seventh and T, "is in a way responsible for the concert. I have one of the few examples on tape of Buck Hill with strings, from a rehearsal for a modern dance suite I did for the Ethel Butler Dance Company. Someone heard that and said, 'We're looking at the tip of the iceberg and it's time to start looking deeper.' "

Thursday's 8 p.m. concert will be taped, as was a 1979 concert. That one ended up being aired on WAMU, somewhat against Wheatley's wishes (since all the compositions were originals). Eventually, he let WAMU air it, more as a favor to the players. The incident inspired a brief poem that seems a good capsule of Wheatley's work ethic:

Sometimes I feel like going fishin'

Cause life is like a can of worms

A lonely musician sitting here wishin'

You'd listen but on my own terms.