ALMOST 50 years later, Richard Sherman clearly recalls the moment he realized the score to "Mary Poppins" was going to be something special.

"I didn't know it until the day when Julie Andrews came to the studio," said the 82-year-old co-composer (with his older-by-two-years brother, Robert) of the iconic musical during a Monday afternoon call to his Beverly Hills home. "She sang 'A Spoonful of Sugar' in her incredible voice. I was sitting in [the recording] booth listening to it, and I was crying. It was magical."

As we all know, Sherman's instincts, and tearducts, were right on the money. The 1964 film version of "Mary Poppins" produced by the Walt Disney Co. went on to become one of the most successful and revered movie musicals ever. In 2006, the live version, staged by Walt Disney-esque uberproducer Sir Cameron Mackintosh, debuted on Broadway.

Tonight, the musical has its Philadelphia premiere at the Academy of Music, where it will run through April 17.

With sterling performances by Andrews (in her film debut) as the enchanted nanny who arrives via bumbershoot to bring love and understanding to a prosperous, if emotionally distant family, and Dick Van Dyke as the impish (and equally magical) chimney sweep Bert, "Mary Poppins" became a multi-generational pop-culture touchstone. It also solidified the Sherman Brothers - or "The Boys" as Walt Disney liked to call them - as "Uncle Walt's" go-to music-makers.

Before "Mary Poppins," Richard and Robert Sherman had found moderate success as songwriters, a trade they inherited from their father, Al Sherman, a tunesmith whose credits included such Depression-era ditties as "You Gotta Be a Football Hero" and "Potatoes Are Cheaper."

The brothers scored during the 1950s and early '60s with "Tall Paul," a hit single for then-Mouseketeer Annette Funicello, and "You're Sixteen," a 1960 smash for rockabilly artist Johnny Burnette (and again in 1973 for Beatle Ringo Starr). They also freelanced songs for Disney films. Hayley Mills sang their "Let's Get Together" in the 1961 hit "The Parent Trap."

Disney, explained Richard Sherman, "saw something in our songs that wasn't in others that were being written" for Disney movies. That undoubtedly led him to take a meeting with the songwriting siblings one day in the early '60s. During the sit-down, Disney handed the Shermans a book by British author P.L. Travers, a series of stories about a somewhat mystical British nanny.

"He said, 'Read the book and tell me what you think,' " Richard Sherman recalled. "We both read it very thoroughly. I thought, 'My God, it's a marvelous character, but there's no plot.' "

Before their next meeting with Disney, the Shermans underlined six chapter titles in the table of contents that they thought could be the basis of a film script. When they returned the book to Disney, Richard remembered, Disney "pulled his [copy] off the bookshelf and opened it up. The same six chapters we pulled out were the same six he had pulled out."

Those stories became the basis for the movie.

From the beginning, said Sherman, he and his brother, who today lives in London, understood how high the stakes were for them. "We decided to really dig in," Richard said. As it turned out, they hit a home run in the top of the first inning.

After forming a number of musical ideas based on their readings, as well as conjuring a basic outline for the film's story, the Shermans returned to Disney's office to audition what they'd written. (Richard is the musician, but both brothers have always shared composing and lyric-writing credits.) One of the concepts they offered was based on the Travers chapter about a poor old woman who spends her days selling pigeon food for "tuppence a bag."

"After hearing what we had, Walt said, 'Play that bird-lady thing again,' " Richard Sherman recalled. "We did, and he said, 'That's what it's all about, isn't it?' "

Disney instinctively understood that the song, which ultimately became "Feed the Birds," wasn't really about a woman and her concern for London's pigeons; its true subject was "a prayer for understanding - be kind, give love. It doesn't cost anything," Sherman said.

Until Disney's death, Sherman added, he would often summon the composers to his office just to have them play "Feed the Birds."

During his interview with the Daily News, Sherman went to great lengths to credit Disney and others whose creative input helped shape "Poppins." He had special praise for arranger Irwin Kostal and his understanding of the early 20th-century English music-hall feel the brothers wanted their songs to invoke.

"Mary Poppins" would be a blockbuster film of the first order, beloved by millions around the world. The Shermans won Oscars for best music, score, substantially original and best original song ("Chim-Chim-Cheree").

Ironically, one person who was anything but delighted with the film was Mary Poppins' literary creator, Travers.

According to "The Boys: The Sherman Brothers' Story," a 2009 documentary made by Richard's son Gregory and Robert's son Jeff, Travers fought the brothers and Disney at every turn during production, which led Robert to describe her in the documentary as "a witch."

Travers "never got with the program," Richard Sherman said. "She never understood we weren't trying to decimate her stories."

Though she died in 1996, Travers' distaste for what the Disney team did to her original stories played a crucial role when it came time to develop the property for the Broadway stage. While much of the production hews to the movie, there is a good deal of new music written by the British team of George Stiles and Anthony Drewe.

As Sherman understood it, Mackintosh told her he couldn't adapt the movie if he couldn't use the Shermans' music. Travers relented, but with the stipulation that any new music had to be written by English composers.

Richard Sherman insisted there were no hard feelings when he learned he wouldn't be creating new songs for the play. He has other projects - his newest musical, "Pizzazz," a tribute to the music of the turn of the 20th century, debuts next week in Santa Barbara, Calif.

And he said he bears the new "Poppins" composing team no malice, describing them as "brilliant."

"You have to be a big boy and not moan, 'Why did they do that,' " he said. "If I did, I'd be Mrs. Travers!"