Oh, say can you ... sing?

For 90 seconds, Marty Ray's ability as a talent scout will be scrutinized by everyone at Fenway Park. Before 36,000 fans can root for the home team, before the umpire can yell "Play ball!" before the Boston Red Sox and New York Yankees can resume their historic rivalry, Mr. Ray will watch as Sabreen Staples, a student at the nearby Berklee College of Music, handles the toughest pitch of the evening: singing the national anthem.

It's a tense minute and a half. Ray, the man charged with wading through hundreds of submissions, searching for as many as 81 musicians to perform "The Star-Spangled Banner" at Sox home games, knows that anything can go wrong. Once, singer Michael Bolton faltered mid-song; the crowd had to carry him through to the end. Tonight, Ms. Staples will be flying without a net - while many amateurs are prerecorded to avoid musical balks, she will be singing live.

But Ray is a pro at calming nerves. "It's best if I don't show much emotion," he says.

The front offices of baseball clubs conjure images of powerful general managers and shrewd scouts, negotiating for high-priced free agents. Yet they're also filled with unseen employees like Ray, who find singers for a pregame tradition as much an institution as the seventh-inning stretch.

The Marty Rays of baseball perform a job akin to wading through an open-call audition for "American Idol." This particular night is Ray's swan song in the position. Once he has handed off the task to his successor, Jahaan Blake, he will move to another post in the organization. For the singers who have filled Fenway's irregular walls with "The Star-Spangled Banner," Ray's steady gaze has been the whole world - an indispensible anchor. Fighting a sound system that, until this year, had a 1.5-second delay, he has coaxed them through heart-stopping renditions of a song notorious for being difficult to sing.

"The Star-Spangled Banner" was first performed at a baseball game during the 1918 World Series. Played by a brass band, it was a patriotic flourish during World War I. It didn't become a fixture at games until World War II. (Congress made it the official anthem in 1931.) Today it has a place in nearly every sporting event. Some like to quip that the anthem's final words are "Play Ball!"

At 6:02 p.m., Staples appears at the edge of the field. With dreadlocks piled high on her head and a yellow chiffon dress stuffed beneath a brown leather jacket, she moves confidently in gold high-heeled sandals. She'll graduate from Berklee this year and has sung twice before at Fenway - once prerecorded, once live. Because of the delay in many stadiums, singers are often pre-recorded. But even this precaution has led to technical difficulties. There was the time when four women opened their mouths to the miscued recording of a male barbershop quartet. In what could only have resembled an identity- theft commercial, they finished out the performance.

Ray catches sight of Staples and walks over to greet her. The tiny park is too small for a green room, so Staples leans casually against the wall that rings the field. "He's making me feel like a million dollars right now," she gushes, stepping away from her entourage to hug him.

Ray has been with the Red Sox since 2002. He began managing the anthem singers in 2004 and has devised his own system for organizing the 350 audition CDs delivered each year. It consists of four "rather ominous looking black albums," each holding 128 CDs, a stack of spreadsheets for scoring them between 1 and 10, and an Aiwa CD player.

Ray doesn't have a baseball background, though he did grow up playing cricket in India. When discussing the anthem, he sounds most like the Boston University English major he once was. "I think good judgment comes from knowledge of the song or poem you're judging," he says, referencing the anthem's 1814 origins as a battle poem by Francis Scott Key.

The live, a cappella performance is a relatively new addition. During the '70s it was customary at ballparks to play any one of five recordings that included versions of the anthem sung by Robert Merrill and the Mormon Tabernacle Choir and an instrumental rendition by the US Marine Band. According to Charles Steinberg,the Red Sox executive vice president for public affairs, the tradition of using local performers at home games was brought to Boston when new owners took over in 2002.

For the most part, the clear, often touching renditions of amateurs are forgotten, swept aside by the event to which they are the briefest prelude. Instead, it's the truly lovely, awful, and humiliating celebrity moments that have stuck. Whitney Houston's transcendent gospel-inspired performance (lip-synced) at Super Bowl XXV in 1991 is considered one of the best. Roseanne Barr was booed off the field in 1990 after her crotch-grabbing, phlegm-spitting effort to emulate the ball players at a San Diego Padres game. "That was probably the lowest of the low," recalls sportswriter Frank Deford.

Ray and a committee of four convene intermittently throughout the year to judge audition CDs on accuracy, musicality, and timing. "Oh, say can you see by the dawn's early fight" is a common point deduction. And while Ray acknowledges he's no expert, it has to sound good: "I'm not going to sit here and pretend I know what a C major and C minor is - but a note is a note, and you have to hit the note." The recording must also be under 90 seconds.

Rarely does anyone who rates lower than an eight make it onto the field. Occasionally you'll hear a 7.5, says Ray, like the wife of a player's brother who barely made the cut - and will remain unnamed.

From a conference room with a startlingly clear view of right field, where the judging occurs, Ray suggests a bit grandly that singing the anthem in this iconic park "may be the steppingstone to a great career."

Has that ever happened?

"Not yet," he concedes. "But we like to believe it will."

Around 7 p.m., Staples takes the field. Ray stands before her, hands crossed. She opens her mouth, the anthem's first words melting over Fenway Park.