A variety of exhibits featuring the music, art, film, television and theater of Belgium will open here April 20 as part of the $4.5-million Belgium Today program.

The events celebrating Belgium's 150th year of independence, will appear in various museums and exhibition halls (including the Library of Congress) from April into the summer. The program was initiated and coorinated by the Belgian American Educational Foundation, Inc., headquartered in New York.

The project is partly funded by the National Endownment for the Humanties -- which gave $670,000 directly to the BAEF and to participating institutions. In addition, funding has been provided by the National Endowment for the Arts (a total of $212,000 for different exhibits), the Belgian government ($2,327,000), and various other sources including the BankAmerica Foundation ($50,000). The Endowment funds must be matched dollar for dollar.

"Belgium is becoming a symbol of the ability of nations in Europe to work together," said Joseph Duffey, chairman of the Humanities Endowment, yesterday afternoon after a press conference at the Belgian Embassy. "We take our relations with Europe for granted. We have tremendocus trade with Belgium. Sometimes commericial relations iwth a country get way ahead of cultural understanding."

Also at the press conference were Livingston Biddle, chairman of the National Endowment for the Arts; Dr. Emile Boulpaep, president of the BAEF; and Belgian Ambassador to the United States, J. Raoul Schoumaker.

The Belgium Today program opens on the Mall at 9 p.m. on April 20 with musically choreographed fireworks to be attended by Belgian King Badouin and Queen Fabiola. Belgian music will be broadcast -- in synchronization with the fireworks -- on WGMS-AM and Fm radio stations. Only those bringing radios stations. Only those bringing radios will be able to hear the music. "Belgian fireworks are the finest in terms of color precision," said Brooke Lappin, program director for Belgium Today.

"It will be interesting to study this funny animal we call Belgium," said Schoumaker, "and see if it flies." After Washington, the exhibit will travel to San Francisco and New York.