There's trouble in River City, if only the townsfolk could see it. But they're too bedazzled by newcomer ''Professor'' Harold Hill's promises of glory in the form of a costumed brass band that will keep the local youth out of the pool hall and on the streets — in orderly formation, of course. Little do they know Hill is a musical illiterate who travels across the country selling band instruments, costumes and instructions to unsuspecting citizens of similar small towns without ever actually hanging around long enough to teach folk how to put them to use.

Only ''Old Maid'' Marian the Librarian, a music teacher herself, suspects that Hill is not all he professes to be. To win her over, Harold — suavely played by the good-looking John Barnes — begins courting her in earnest and even pays special attention to her shy little brother, Winthrop, who barely speaks to anyone because of an embarrassing lisp. As Marian witnesses the effect Harold's positive attitude and personal charisma have on Winthrop, she starts to doubt her misgivings. Should she expose him to her fellow citizens, or trust him with her heart?

Composer Meredith Willson based ''The Music Man'' on his own small-town American boyhood, circa 1912, but those of us who dwell there today will have no difficulty relating to the cast of characters, especially when the acting on stage is this good (the opening night audience gave a standing ovation). Ralph Schwalm is a windbag of a mayor and Vicki Montesano exudes a comical hauteur as his wife, Eulalie McKechnie Shinn, River City's ''Grande Dame.'' Amanda Salvatore sings the Marian role with relative ease and can act, too. Patrick McGee is just adorable as Winthrop. The rather large and energetic supporting cast, splashily attired in colorful turn-of-the-century outfits by costumer Brenda McGuire, is another bright spot.

The show is directed and choreographed by Ann Marie Squerrini. Her clever staging of the musical numbers makes the stage seem much larger than it is. She is aided by picture postcard-inspired scenery designed by Rafael Salazar. Happily, an actual band, directed by Nancy Shumaker, plays the score, which includes such Broadway favorites as ''Gary, Indiana,'' ''Goodnight My Someone,'' ''Till There Was You'' and ''76 Trombones.'' My only quibble — and one I frequently have at the playhouse — is that the band sometimes plays over the voices of the singers. Tone it down, please!

Those who know and love ''The Music Man'' cannot help but enjoy this classic production of an old-time favorite. And those who haven't, might just want to. It offers a respite, however brief, from the darkness of our troubled world.

''The Music Man,'' 8 p.m. Friday and Saturday, 6 p.m. Sunday, through Aug. 7, Pennsylvania Playhouse, Illick's Mill Road, Bethlehem. Tickets: $18; $15, seniors and students Friday and Sunday only. 610-865-6665.

Marguerite Smolen is a freelance writer.

Jodi Duckett,
Arts and Entertainment Editor
jodi.duckett@mcall.com
610-820-6704