It took a bit of cogitation and nosescrunching, but 7-year-old Mark Muffoletto finally hit on the right words for "Museum Piece," an avant-garde composition for cello, flute, recording tape and slide projections.

"It sounded," Mark said, as he sat with his older brother in the University of Maryland's Tawes Recital Hall, "like an elephnat trying to make a sound, except that the elephant had laryngitis, and he also had his trunk cut off."

Not that Mark disliked the Washington premiere of the mixed-media composition by New Yorker Carman Moore -- a piece replete with abstract expressionist paintings beamed on a screen as two musicians competed with heaving breathing and heart beats. Mark even found merit in the mariba solo and dance and choral work that followed.

"It was just good music," The Baltimorean declared.

So it went the other day at the Classical Vibes Children's Program, an offering of the University Community Concert Series, now in its third year. The program, says UCC staffer Eva Hornyak, is designed to expose kids in the Washington area to music they'd otherwise miss in the Top 40 and on television.

But unlike the staid and proper concerts that some adults seem to favor, Classical Vibes gives the audience a chance to talk back to the performers and occassionally composers -- browbeat them, if necessay -- when the music stops.

This Saturday at 2, for instance, the University Opera Theater will present a shortened, but fully staged and costumed version of Mozart's "Marriage of Figaro," in Tawes Recital Hall. (Ticket's are $4 for kids and $5 for adults; call 454-6534 for information.) During intermission, the singers will move into the corridors to field questions.

The other day, "Museum Piece" was much on Mark Muffoletto's mind.

"Why were the pictures so strange?" Mark demanded of Carman Moore, who has composed on commission for the New York Philharmonic. "They just looked like big blocks of paint."

"Well," the composer said as he sat on the edge of the stage, "you can just think of the colors and what they remind you of. Maybe they're tires or autumn leaves."

"But to me," Mark persisited, "it just looked like someone had paint on his shoes and walked all over them."

Moore laughed. Mark frowned.

"The great thing about kids," Moore said later, "is that they don't bring a whole lot of stuff to a performance. They don't say, 'That sounds like Bartok or this sounds like Stravinski.' They just come to listen."