Five orchestral works by American composers, all of which have had their premiere performances within the last two years, have been accepted as finalists in the annual Kennedy Center-Friedheim Competition for new American music.

They will be heard in a free public performance at the competition finals in the Kennedy Center Concert Hall at 6 p.m. Saturday, Oct. 2. This performance, with Peter Eros conducting the Peabody Conservatory Orchestra, will be taped by National Public Radio and the Voice of America for later broadcast.

The new compositions, selected from a field of 80 entries, include one work by a young Washington composer that had its premiere performance here in May during the Inter-American Music Festival: Symphony No. 1 ("Age of Victory") by Thomas Ludwig.

Other finalists include two of America's best-known living composers: David del Tredici ("Happy Voices") and Domenick Argento ("Fire Variations"). The program will also include a guitar concerto by Ivana Themmen of Ridgefield, Conn., and "Avanti!" by Gundaris Pone of New Paltz, N.Y.

The winners, who will be awarded prizes of $5,000, $2,000 and $500, will be chosen by a jury consisting of Irving Lowens, former music critic for The Washington Star and dean emeritus of the Peabody Conservatory; Richard Bales, composer and director of music for the National Gallery; and Frank L. Peters, music critic of the St. Louis Post-Dispatch.

The awards were created in honor of the late Arthur Friedheim, pianist, and are funded in part by a grant from the Eric Friedheim Foundation, established by his son. The competition is held for orchestral music in even-numbered years and for chamber music in odd-numbered years.