Some singers have a falsetto pitch that can break glass.Barry Gibb of the Bee Gees has a falsetto pitch that sets off female screams. Every time he hit that pitch at the Capital Centre last night, squeals split the air.

One of the screamers was 18-year-old Alice Severe of Baltimore. "I just can't help it," she said in a hoarse voice. "it just comes out. I want them to know I'm their fan. Nothing can top them -- not the Beatles, not nobody." She broke off to leap with fist in air at the opening of "Can't See Nobody."

The Bee Gees came to the Capital Centre last night for a two-night stand, the 31st stop of a 38-city tour. The long trek, which began June 28, ends Oct. 6 in the group's adopted home town of Miami.

The tour caps two of the most triumphant years in pop music. The Bee Gees' soundtrack for "Saturday Night Fever," released in late 1977, rewrote the section on album sales in the Guinness Book of World Records. The three native Australian brothers followed that up with this year's No. 1 album, "Spirits Having Flown," and with the current tour of sold-out arenas.

The Bee Gees set their sales records by crossing the normal boundaries between ages, races and nations. Much of the 30 million sales for "Saturday Night Fever" came from outside the usual Anglo-American youth market for pop records.

The median age at last night's show was far higher than one would expect. There were grade-school kids, to be sure, but most of the audience seemed to be couples in their late 20s or 30s, with or without children.

In the Nicolettos family of Laurel, for example, it was 35-year-old Ermione who wanted to take her 10-year-old daughter, Tina, not the other way around. It was Ermione who got in line at 7:30 a.m. the day tickets went on sale at 10 a.m. at the Capital Centre. She didn't get her tickets, until 11:30.

The screaming at last night's show was so loud that it obscured the lyrics at times, But otherwise, the crowd was one of the most orderly for a Capital Centre rock show in recent memory. The aisles stayled clear; no one rushed the stage. No more than a few even stood up until the last few numbers.

Most of the audience was neatly dressed in suburban slacks and sweaters. This was one of the few Capital Centre music crowds you could put on prime-time TV with no worries.

The Bee Gees, playing to the crowd, used smoke bombs and laser beams that won ovations with each appearance. The three singers wore silver aviation jackets, partially unzipped over their hairy chests. As the show wore on, the zippers came down to escalating screams. When Barry did his solo number on "Words," the screams shifted as he turned to face different sections of the arena.

The Bee Gees seem to have healed the musical generation gap in many families. Shelley Himelfarb of Potomac and his daughters, 7-year-old Jill and 9-year-old Lisa, were equally enthusiastic about the show. "I agree with my father on most music," said Lisa.

Twelve-year-old Kimberly Morahan of Laurel was in Miami on vacation when she searched out Barry Gibb's new $1.5 million house in Miami Beach. The singer wasn't home. So Kimberly put a note in his mailbox saying she was upset that she couldn't get tickets for the Capital Centre show and that she didn't meet him in Miami. When she returned home to Maryland, two tickets were waiting for her in the mail. She took her mother to the show.

Also at the concert were couples such as 56-year-old Silver Spring bank manager John Miller and his wife, Kathryn. "We saw 'Saturday Night Fever' three times," said Kathryn Miller. "We like to dance to their music."

"You're only as old as you feel," her husband added. "After we saw 'Saturday Night Fever,' we went out and took disco lessons."

The merchandisers were also cashing in on the fever. There were buttons and posters for $3, color programs for $4, and a variety of necklaces and T-shirts for sale.

One concessionaire, 21-year-old Jennifer Hahn of Riverdale, danced in her orange uniform with "Popcorn" and "Hot Dogs" printed on it during "Nights on Broadway." She estimated that she had $900 stuffed in her apron pockets.