Vaughan, Marsalis at the Pops; 'Cinderella'; Art Newbury Street

Some Bostonians are astonished by the appearance, in their midst, of the schmaltz and glitter of Copley Place. How, in a town of such high decorum, where the Lowells speak only to Cabots, could such a shoulder-rubbing, polyglot kind of indoor picnic ever have been conceived?

They obviously haven't been to an Opening Night at the Pops, where incongruity is the order of the day.

Not that the 99-year-old Boston Pops Orchestra (drawn largely from the Boston Symphony Orchestra personnel) was not in top form at the May 1 gala. Not that John Williams did not do a masterful job of conducting with both panache and nuance (he did). Not that Wynton Marsalis didn't play the Haydn E-flat Trumpet Concerto with astonishing delicacy and brio (he did), nor that Sarah Vaughan didn't sing ''Misty'' to perfection, team up splendidly with Marsalis on ''September Song,'' and produce an incomparable rendition of ''Send in the Clowns'' (she did). Not that the audience didn't lap it up.

But consider the incongruities. Symphony Hall, staid in its molded plaster cornices and busts of musicians past, was arranged not unlike a set for a Kansas barn dance: seats stripped out and replaced by tiny tables for the pre-concert picnic dinner. On each, a tablecloth - and a potted flower in crumpled tinfoil. Dinner came in a fancy basket - with plastic utensils. When the diners (who had paid as much as $120 for the privilege) had finished, uniformed waitresses cleared - by tossing everything into huge plastic garbage bags carried from table to table. And if some people listened, others talked and laughed during the music - then bolted down the aisles to hug friends during the intermission.

And despite the faces of the musicians - some of whom looked, during the wing-ding show-tune final section, as though they were smelling something pretty awful - there was an air of childlike good humor to it all. And why not? Why not save the brightest for last - a sharply directed and precisely delineated Sousa march, during which a great American flag unfurled above the orchestra and balloons came raining down on the audience? Why not have grown men and women groping under tables for balloons and popping them vigorously as the orchestra crashed to a finish? Why not have them gather up stacks of baskets and take them home (the plants, too) at the end? After all, there aren't many Lowells and Cabots left to talk to.