Washington's jazz-fan base will increase by about 4,000 this week as the International Association of Jazz Educators holds its 18th annual conference, for the first time in the nation's capital. They will gather at the Sheraton Washington Hotel for a convention whose theme is "Celebrating Duke Ellington" and whose agenda will include concerts, clinics, seminars, research papers and award presentations.

Twenty years ago, such proceedings would have been unthinkable, not because IAJE didn't exist, but because jazz education was an overlooked stepchild in the nation's music curricula. "As late as the mid-'60s, there were colleges where you could be expelled from the music school if you were caught playing jazz in the practice room," says IAJE Executive Director Bill McFarlin. "Jazz simply was not respected as a viable art form worthy of study."

At a 1968 Tanglewood symposium, band leader Stan Kenton and composer-pianist Billy Taylor presented position papers expressing their concern at the shocking absence of jazz in those curricula; soon afterward IAJE was formed. "By the mid-'70s, over 100 colleges had accepted jazz studies programs," says McFarlin. "Today there are over 1,000 colleges and universities and over 15,000 high schools that have some kind of jazz program."

More than 100 artists and groups will appear at this week's concerts and clinics. Tomorrow, everything is free and open to the public until 6 p.m., including the inaugural Herb Alpert Jazz Endowment Awards ceremony at 11 a.m. and the 1991 jazz Grammy nominations announcement at 11:30. A number of $15 tickets are available at Ticketron for evening Sheraton Ballroom concerts tomorrow through Saturday. Also tomorrow, the Great American Music Ensemble, directed by Doug Richards, will present an all-Ellington program, followed by a tribute to Taylor (who will also perform). The Friday lineup includes the Max Roach Double Quartet, the Oleg Lundstrem Big Band from the Soviet Union and the Bob Mintzer Big Band with guest Louie Bellson. On Saturday, it's Lester Bowie's Brass Fantasy, Bobby Watson & Horizon, the Rick Margitza Band and Steps Ahead.

There will also be free concerts tomorrow through Saturday on the lobby showcase stage at noon, 2, 4 and 6 p.m., featuring professional and school groups from around the world, some pro jam sessions, as well as local performers such as the Keter Betts Quartet (tomorrow, 6 p.m.) and vocalist Ronnie Wells with the Ron Elliston Quartet (Saturday, 4 p.m.).

Twenty years ago, the jazz profile at the Smithsonian was not particularly high, either, and it's a measure of the winds of change at that august institution that a number of IAJE's Ellington sessions are being presented in cooperation with the National Museum of American History. Of course, Ellington is not only one of the world's greatest composers but a native son; several years ago, the Smithsonian expanded its jazz collection with a major acquisition of Ellington musical and professional archives, including several thousand mostly unpublished compositions. At 2 p.m. tomorrow, Gunther Schuller will present the keynote address, "Duke Ellington as a Major American Composer" (Virginia Room); at 4 p.m., Ellington scholars Ed Green and Andrew Homzy will present papers (also in the Virginia Room; both these sessions are open to the public).

The IAJE conference will be one of the largest gatherings of Ellington scholars, and after it's documented and recorded, it will further enrich the Smithsonian's Ellington collection, some of which is on view on the museum's third floor in "Duke Ellington, American Musician," an exhibit that will travel the nation starting next year.

Throughout the conference there will probably be lots of talk about the Smithsonian's in-progress Jazz Masterworks Editions, the first attempt at producing authoritative, scholarly transcriptions of recorded ensemble jazz for both professional and amateur musicians, scholars and, of course, educators. Over the next five years, the Smithsonian, along with Oberlin College, will produce 20 volumes focusing on the swing era of the '30s and early '40s and the crucial orchestral works of Ellington, Count Basie, Fletcher Henderson and others.

Eventually, the plan is to preserve on paper much of the accumulated jazz repertoire of the past 70 years (including transcriptions of the influential "Smithsonian Collection of Classic Jazz"). The focus on the swing era is a natural choice not only because jazz was "popular" then, but because the textural complexity and emotional depth of music from the big bands is a match for much classical concert music.

The Jazz Masterworks Editions program, to be discussed at 10 a.m. tomorrow by a Virginia Room panel, will serve many purposes. Not only will it allow classic jazz to be performed live in the manner of European-style classical music (hopefully by a new wave of jazz repertory ensembles), but it will upgrade the literature currently used in schools. According to McFarlin, "Much of what's been available is not the classic literature from the Ellington or Basie libraries. It's an environment controlled by publishers who published what they thought would sell, like jazz versions of popular television themes. As a result of the lack of a broad-based repertory to pull from, there was probably a lot of mediocre music out there being played over and over again, which did not necessarily add to the credibility of the existing jazz education movement. Educators today expect better literature from the publishing companies."

Part of that may be because an increasing number of those educators are drawn from the ranks of performers, particularly at the collegiate level, though McFarlin points out that there are also more jazz components in general music education programs, "so when they graduate they have at least some background in jazz."

The Sheraton Ballroom will also be the site of a Sunday tribute concert (sponsored with the Charlin Jazz Society) honoring this year's American Jazz Masters -- Clark Terry, Andy Kirk, Buck Clayton and Danny Barker -- each of whom will receive a $20,000 fellowship from the National Endowment for the Arts. The concert will feature the Hubert Laws Quintet, Judy Carmichael and Mingus Dynasty with Wynton Marsalis as emcee. Admission is free, by ticket only; for information call 202-682-5445.