For 35 years Richard Bales has been putting together annual festivals of American music for the audiences that gather in the Garder Courts of the National Gallery. This year's eight programs will be heard on the Sundys bounded by April 9 and May 28.

As music director of the gallery, Bales will open and close the festival with orchestral concerts. In between there will be a choral program; and evening with the Madison String Quartet of Colgate University; Regina McConnell, soprano, and two pianists, Wayne Smith and Richard Becker.

There will also be the unusual situation of a program by the Huntingdon Trio, whose three musicians play four instruments. Diane Gold plays flute and Lloyd Smith cello. But since Rheta Smith plays both oboe and piano, the trio is prepared to offer music calling for a far larger number of instrumental combinations than if Smith were a mere single-threat player.

Within the framwork of the eight programs, Bales will offer four world premieres: two symphonies and two works for the flute-oboe-cello-or-piano combine. The symphonies are the ninth by Walter Spencer Huffman and the second by Frederic Goossen. The Huntingdon Trio's new music will be a set of Four Nocturnes by David Loeb and Reflections by Lani Smith.

The festival will also present nine first Washington performances. These will range from the 19the-century symphony by George Frederick Bristow to a sonata by pianist-compsoer Becter, whose program will also include works that have already entered the standard repertoire, such as the Barber Sonata and George Crumb's Five Pieces. Becker will also play music by David Del Tredici, whose "Lobster-Quadrille" aroused divided opinions two weeks ago among National Symphony Orchestra subscribers.

Wayne Smith, the festival's other pianist, will play an entire program of music by JOhn Powell, the Virginia composer whose sonatas carry such fanciful titles as "Noble," "Psychologique" and "Teutonica." Powell will play the allergro movement from the first of those and the entire "Psychologique," as well as the suite "In the South" and "Circassian Beauty."

Among the other works receiving their first local hearings will be string quarters by Dexter Morrill, Marc Neik-rug and Hsueh-Yung Shen, who calls his "Fout Characteristic Movements." The Huntingdon three-foursome will bring the first Washington performance of Burrill Philips' Huntingdon Twos and Threes, "Cirrus," by Sam Dennison and "Poem of Soft Music" by Larry Nelson.

In her song recital, which lists Samuel Barber's Hermit Songs, together with songs by John Duke, Thomas Pasatieri and Aaron Copland, Regina McConnell will give the area premiere of five songs from "Flame and Shadow," by Bain Murray.

Bales has arranged for a choral program to be sung by the choir of the National Shrine, whose director is Robert Shafer. On that evening, music by two of Washington's finest composers in this idiom will bring hearings of various scores by Russell Woollen and the late Robert Evett. With two of his own compositions on the final program, Bales is thus giving proper attention to composers of this city.

There is a fine range of compositional styles in the fertival which begins tonight. With such names as Copland, Barber and Hanson, the younger Rorem, Crumb and Del Tredici, much of the finest musical accomplishment of this century's American music will be strongly represented. At the same time, the presence of such unfamiliar names as Morrill, Dennison, Loeb and Shen assures those who hear the entire festival of introductions to music that may travel in new directions or perhaps continue what seems a present trend, that of synthesizing the best of the past half century.

All of the concerts are, as always at the National Gallery, free. They will be given in the East Garden Court, and, as usual, broadcast live over Station WGMS.