It was nothing if not a hectic schedule for 22 members of the Boy Singers of Maine, who traveled farther than any other group to sing at this year's Pageant of Peace. Starting Sunday evening, members of the chorus:

*Sang in Portland with the Portland Symphony Orchestra.

*Boarded a chartered bus for an overnight trip to Washington, arriving early yesterday.

*Toured the FBI and had lunch, arranged by the Maine State Society of Washington at Fitch, Fox & Brown restaurant in the Old Post Office Pavilion.

*Sang, nattily attired in red turtleneck shirts and blue blazers, on the Pavilion stage.

*Napped at a hotel.

*Sang at the Pageant.

*Boarded the same bus for the second overnight trip in a row, back to Portland, where they were due this morning.

"The bus wasn't too comfortable," said Matthew Whitney, 12. "I like everything I've seen so far, especially the FBI," said Andrew Bisson, 11. By the standards of most tourists, he hadn't seen much.

Michael Braz, the chorus director, said the boys jumped at the chance for the whirlwind trip. "They're hams," he said. "They love an audience." Celebrating a Birthday

There was music of another kind in Washington on Sunday evening. Celebrating her 100th birthday, Washington-born Flora Brylawski, sang a little-remembered song, "Love, Here Is My Heart," that many years ago she sang professionally at the annual employe banquets of the Washington Star. A grandson, Samuel Brylawski, who works in the music division of the Library of Congress, located the sheet music.

Born Flora Bernheimer, she remains mobile and alert. The first Washington home she remembers was on the south side of B Street -- now Independence Avenue SW -- just west of Seventh Street, where the Federal Aviation Administration building now stands.

In 1909, she married Baltimore-born Julian Brylawski, an early motion picture exhibitor who built the Earle (now Warner) Theatre. He died in 1977 at age 94. Since soon afterward, Mrs. Brylawski has shared a household in Annapolis with a longtime family friend, former Washington lawyer Philip Ershler, now 96.

The reception was held at the Washington Hebrew Congregation. Henry Brylawski, a son, said his mother was on her feet mixing with the guests for nearly two hours. Signaling Distress

The American flag, flown upside down, is a recognized signal of distress. Marcia Pape, a Capitol Hill resident, said she saw the flag so flying at the shelter for the homeless at Second and D streets NW, run by the Community for Creative Non-Violence, that the government is trying to close.