The "largest and most musically diverse" commissioning program for American composers has been announced by Meet the Composer Inc., the Lila Wallace-Reader's Digest Fund and the National Endowment for the Arts.

Composer John Duffy, president of MTC, and Jane S. Moss, executive director, have designed a first-year program that has resulted in grants from $6,000 to $45,000 to support commissions for 39 composers of concert music, jazz, opera and music theatre.The most impressive aspect of the grant process is that it required forming 20 consortia comprising 60 arts organizations. Since all consortium members must perform their commissioned works (and possibly those of other members), each composition is guaranteed a diverse, nationwide audience.

Musical organizations in cities large and small are involved in the new project. Three of the "biggies" - the Chicago and St. Louis symphonies and the New York Philharmonic - joined in commissioning a new work by one of today's "hot" composers, Joan Tower.

Three other big name composers - David Del Tredici, Leon Kirchner and Mel Powell - were recipients of the largest grant, $45,000, for a concertium composed of the New Jersey Symphony and the St. Paul, Minn., and Los Angeles chamber orchestras.

The second most generous grant, $42,000, went to the Oregon, Syracuse, N.Y., and Denver Symphonies for commissions to Alvin Singleton, Tomas Svoboda and Deborah Drattell.

Tower has been composer-in-residence with the St. Louis Symphony and conductor Leonard Slatkin will conduct her new work with orchestras in Missouri, Illinois and New York. Like Tower, Stephen Albert has served two years as composer-in-residence with the Seattle Symphony, which, under Gerard Schwarz, has won wide recognition due to a series of superlative recordings for the Delos label.

Albert was commissioned to provide a new clarinet concerto for virtuoso David Shifrin by a richly mixed consortium consisting of the Seattle Symphony, the Toledo (Ohio) Symphony and the incomparable Philadelphia Orchestra. Albert, quite possibly the happiest composer of this year's rich selection, has just been appointed to the composition department of the Juilliard School.

Southern orchestras are very much involved in the composer's project. James Oliverio was commissioned by the symphony orchestras of Macon, Ga., Chattanooga, Tenn., and Savannah, Ga., as well as the Columbus Symphony in Ohio and the Eugene Symphony in Oregon.

Chamber music was not neglected either. Andrew Imrie, Jalalu-Kalvert Nelson and Barbara Kolb are sharing a $26,000 grant for new works to expand the repertory for piano, violin and cello.

Probably the work most likely to generate major attention in national and international circles is the new opera to be composed for the Brooklyn Academy of Music's Next Wave Festival and the periodic Los Angeles Festival by the same team who gave us the most recent pop-hit opera "Nixon in China."

Composer John Adams' newest opera was given a $22,500 grant and he and his "Nixon" collaborators, librettist Alice Goodman, director Peter Sellars and choreographer Mark Morris are expected to produce another hit in time for the Next Wave Festival in October of 1991.

Deborah Drattell's composition for the Oregon, Syracuse and Denver symphonies will be a work for chorus and orchestra based on Edgar Allen Poe's short story "The Pit and the Pendulum."

Dominick Argento is one of today's most performed composers and a new piece for a capella chorus has been commissioned by a large consortium of choral groups in Santa Fe, N.M., San Francisco, Houston, Connecticut, Ohio and Illinois.

Finally, a major grant of $27,000 was given to three of the finest professional choral ensembles - San Francisco's Chanticleer, the Twin Cities' Dale Warland Singers and New York's Musica Sacra - to perform the works of Bernard Rands, Anthony Davis and Peter Schickele.