Next Saturday night's first "International Theater Costume Ball" at the Sheraton Park is a production of ATA.

What is ATA?

The American Theater Association, headquartered at 1000 Vermont Ave. NW, describes itself as "the nation's umbrella for the non-commercial theater." It is a gathering together of eight national organizations, accomplished in recent years.

That may sound simple, but simple is the last thing ATA is.

Nothing in this huge United States is simple nor can it be easily wrapped up in a nutshell description, illustrative as that umbrella simile is. There are thousands of local organizations within this grouping and, bound together, they add up to more than the sum of their parts. Like Republicans and Democrats, unions, chambers of commerce, leagues of this, associations of that, they are aligned to create a self-serving, even a political, force.

Rooted in educational circles 42 years ago, ATA has expanded by enveloping like-minded groups which, autonomous themselves, gain strength in union. Consider its eight divisions:

ACTA refers to the American Community Theater Association. There are literally thousands of these in the 50 states and territories, some employing professional directors, technicians and guest stars. Some perform in buildings they have financed themselves. Some mount only a production or two a year, some have subscription plans for as many as eight.

ATAA is the Army Theater Arts Association. Presenting as many as 25,000 performances a year, it (barring Soviet disclaimers) is thought to be the largest theatrical producing organization in the world, playing in humble or fairly grand theaters, including dinner theaters on many bases.

UCTA is the University-College Theater Association, best known for its annual American College Theater Festival presented in 13 regional centers and culminating every spring in the Kennedy Center.

CTAA is the Children's Theater Association of America. For too long, Europeans, notably the Russians, have taken children's theater infinitely more seriously than we. In the past decade or so, leaders from St. Paul, Nashville, Albany and Seattle have been disputing the idea that anything will do for the kids. New plays are actively encouraged. Details of production are aimed at the finest professional level.

U/RTA means University/Resident Theater Association. These campus theaters - including those in Ann Arbor, Mich.; Princeton, N.J.; Palo Alto, Calif., Hanover, N.H. - boast resident companies of professionals who both perform and teach, an area which seems to be on the rise in both public and private colleges.

SSTA is the Secondary School Theater Association, meaning pretty exactly that, pre-college theater, independent of the curriculum but led by trained teachers, even veterans of the art.

NAST is the National Association of Schools of Theater. There are comparatively few of these, which can be considered conservatories, teaching only theater arts.

ATSL is the American Theater Student League, now in a re-organization period. Its concept is to locate jobs for college students as individuals with training.

Further, there are subgroups. There is BTP, the Black Theater Program. The nine-issues-a-year ATA magazine, Theater News, this year devoted one issue to deeply considered thinking on the respect overdue the black middle class. Overlooked in what basically is a middle-class nation, this area was examined with fine feeling in Jeanne-Marie Miller's report, one far more penetrating and probably more accurate than the Yale Review's of a year earlier.

Another issue spotlighted a Senior Adult Theatre Project, a new creative exploration. SAT was the only arts group represented at the National Council on Aging last spring.

For administrative convenience, ATA divides the nation into 13 regions, each having its own annual conventions in different locales. Quieter think time is found for leaders in biennial conferences at Wingspread Center, Racine, Wise.

Having attended national and regional meetings, I've learned the most at the regionals. From discussion panels, performances and auditions one gleans the vitality of intelligent ambitions found only rarely a decade ago. These groups are fairly familiar with one another's work, a familiarity which makes the meetings more relaxed, however acrimonious. Visiting guest speakers stimulate new ideas.

National meetings of all kinds inherently are chaotic. Four New Orleans days last summer listed over 400 different sessions attracting over 14,000 participants and observers. Generalizations of broad topics and particularization of minutiae ranged from effects of Proposition 13 to Maude Adams' teaching career and the on-going restoration of a 6,000-seat Roman theater in Spain.

Taking office as ATA president this year, Tulane University's Milly S. Barranger accented ATA's professionalism.

Though ATA claims not to be commercial, it is professional. Employes through all eight divisions are trained professionals who earn their living in the melange of crafts which create theater.

While non-commercialism is a luxury in this largest organization of American theater, realities must be faced and there are strong ties to veterans of the commercial area.

One of Saturday night's judges for the costume ball is Joshua Logan, whose triumphs have included such commercial successes as "Mister Roberts," "South Pacific" and a score more. With Logan will be his wife, Nedda Harrigan, whose father, of Harrigan and Hart, strongly influenced our late 19th-century theater.

Another judge will be Ezra Stone, radio's Henry Aldrich in his youth and now, bearded and gray, a force for nurturing new playwrights. Stone's wife, Sara Seeger, a Washington amateur actress who turned professional, personifies this link between the commercial and noncommercial.

It was a stricly commercial star, Peggy Wood, who, inspired by guest performances on several campuses, literally created the American College Theater Festival and no one valued sold-out houses higher than Wood.

Thus Barranger's accent on professionalism is accurate and should be highligted. To be noncommercial does not mean to be non-professional.

This tone of quality is the major concern of ATA's executive director, Jack Morrison. Morrison's beginnings were in the rough commercial world and he can speak that language. As the continuing, Washington-based voice of ATA, Morrison has made quality his major theme.

It was Morrison who first attempted to point out the red herring of an incipient populist-vs.-elitist battle. There has been a political temptation to make majority activity seem oppressed by elite standards.

"Quality," Morrison remarked, "is a matter of valuing with peer judgment of professionals. It's not always perfect, but it's served pretty well down the centuries. What else is there?"

This priority for quality must be accorded precedence over non-professional standards. It seems a step in maturity for the umbrella organization to be accenting quality, through a president who serves but a year and a continuing officer who bridges administrations.

Thus, while ambassadors and students, professionals and non-commercials are frolicking about in costumes and dance Saturday night to raise organizer Rose Robison Cowen's goal of $50,000, it's not just all in fun.

In back of the ball is the idea that the commercial and non-commercial theaters are not so far apart. In both, professionalism is the road to quality.