When the much-anticipated annual Bands by the Bay tournament steps off on Saturday, 19 bands are expected to go tuba-to-tuba to earn bragging rights - and a few trophies for the dusty front hall display case .

It may not be what Professor Harold Hill of "The Music Man" had in mind when he envisioned 76 trombones, but there'll be enough razzle-dazzle, funky costumes, props, flags and flashy instruments to put him in a swoon.

Two of the 19 bands won't be competing, not this time. Since Broadneck High School is hosting the event, its band plays last and is not judged. South River High's band will be there to show community support.

But there will be competition anyway between the Gerrior sisters.

They're twins, possibly identical twins - no one knows for sure. Diane Gerrior-Manning is the band director at South River. Sandra Gerrior Balderson, younger by five minutes, is Broadneck's band director.

Aside from their hair color, they could be mirror images.

"I may be younger," zinged Ms. Balderson, "but I had higher SAT scores. Mom told me. She didn't want to hurt your feelings."

Her sister laughed at the sibling ribbing.

Ask one a question and you're likely to get the answer in stereo from both.

They were born on Hospital Point on the Naval Academy grounds - they won't say when. "We're old enough to know better," one twin opined saucily. "And too young to care!" they both finished.

Their father played in the Navy band. While they credit him for their talent, "mother deserves credit for carting us everywhere," Ms. Gerrior-Manning pointed out.

The two grew up in Eastport and played in the Eastport Elementary School band. Mike Svec was their director at Annapolis High School.

The twins have a brother four years older.

"We were born on his birthday," Ms. Gerrior-Manning said. "He says we were the worse birthday gift he ever got."

They both chuckled at their sisterly teasing.

After high school, they headed to East Carolina University together, even though their parents insisted that they live in separate dorm rooms. They went along with that - but their rooms were side-by-side.

They admitted to dating a pair of twin boys in college. "Thad and Chad!" they giggled in stereo.

"People in restaurants did double takes," said Ms. Gerrior-Manning. "It lasted a semester."

Twin pranks, like switching on class breaks in sixth grade to confuse teachers, continued into adulthood.

In 2001, Ms. Balderson took her band to London. Ms. Gerrior-Manning went along too. When her sister woke up one morning too sick to march on the field, her big sister took her place in a parade and a BBC radio concert.

In preparation for the tournament, the Broadneck band is practicing for several hours every day after school and four hours on Saturdays. The South River band is a little more laid-back, meeting once a week.

Since late spring, Broadneck has been working on the music and lots of new dance steps for their show, "Planet Earth: Ocean, Land, Air," with music from the video game "Final Fantasy." Special silks were designed and new costumes are on order.

The band has won regional competitions for the past five years and finished consistently in the top 10 of Group IV bands on the East Coast.

South River's band is similar in size to Broadneck's, but differs in its goals.

"I don't like to compete," said Ms. Gerrior-Manning. "We're a football band, an entertainment band. We're doing selections from 'Mama Mia' - songs like 'Dancing Queen' and 'The Winner Takes It All.' "

The band will wear its classic uniforms, but the guard will wear flowing purple asymmetrical tunics over black pants.

Ms. Balderson and a committee composed of assistant band director Matt Heist, drill designer Mike Ashmead, percussion instructors Ron Frederick and Tim Beall and guard instructor Laura Fitzhugh decide what the Broadneck band plays from year to year.

"Uh, I'm a one-man show," Ms. Gerrior-Manning said with a shrug.

The South River band enjoys marching in parades and Veterans Day ceremonies and looks forward to entertaining in exhibitions and tournaments.

"We're that band, too," noted Ms. Balderson. "But we've taken it to a different level where we are a competitive marching band."

Not surprisingly, the two live close to each other. Ms. Gerrior-Manning lives in Cape St. Claire and her sister lives in Woods Landing near the Bay Bridge.

There is one difference. The older sister plays the flute and the younger plays the clarinet.

"I wanted to play the trumpet," sighed Ms. Gerrior-Manning, "but dad said it wasn't a girl's instrument."

Eerily, like Kewpie dolls in a shop window, they rolled their eyes in the same direction.

Bands by the Bay will be held at 11 a.m. Saturday at Broadneck High School on Green Holly Drive in Cape St. Claire.

Wendi Winters is a freelance writer on the Broadneck Peninsula.