"You must know the nature of the choral animal -- this is a highly unusual and significant event happening here," remarked Paul Hill, conductor of the Paul Hill Chorale, as he fidgeted nervously.

More than 150 singers, arriving fashionably late to "Summer Sings," were considerably less uptight than the creator of this community sing-along, which was held at the YWCA Penney Auditorium last night.

The participants queued up outside the auditorium, trading their driver's licenses for rented scores.

"Anyone is eligible to come," publicist Lynn Fitzhugh explained. "But mainly people who can read music and follow the scores. We sent out yellow fliers to the different choral groups. But mostly we depended on word of mouth."

The presence of two other top choral directors--Norman Scribner, conductor of the Choral Arts Society of Washington, and Robert Shafer, conductor of The Oratorio Society of Washington--seemed to confirm Hill's assessment that the normally "angry, competitive" choral groups gathered in a "spirit of strong, cooperative fellowship."

Scribner christened last night's program, the first of four this summer, with Brahms' German Requiem. Scribner, who recently directed a performance of the Requiem at the Kennedy Center, surveyed the assembly, then introduced Paul Hill Chorale member Rotraut Bockstahler to lead a rote-and-repetition session of the German text.

An obviously envious Shafer offered the aside, "I'm glad Paul thought of this idea--I've been wanting to do this for years!"

"The glory of the singer is in the long notes!" Scribner admonished the singers. By this time, he was visibly working up a sweat, which soaked his T-shirt and set him to stamping his foot while his baton jabbed the humid, stuffy room. The sopranos occasionally wandered off beat; pianist J. Reilly Lewis, director of the Washington Bach Society, settled in.

Hill, worried at first about time constraints, removed his watch and waved it at Scribner. But once the sing-along began in earnest, affording baritone Richard Dirksen and soprano Kathie Gaus-Woollen their solos, Hill relaxed, happy with the results. "Pretty good for a pickup choir," he whispered.