M. Karen Smith answered the knock at her door in Vandenberg Village on Monday, and found her driveway a splash of orange, blue and green.

Star-covered balloons anchored by long strings waved in the brisk wind and seven musicians readied their instruments.

“Happy birthday,” said Mike Pakaluk, director of the Cabrillo High School band, by way of explanation to a surprised Smith, who watched with a cell phone to her ear — a three-way call with her daughter and granddaughter.

“One, two, three, four,” Pakaluk said.

He hoisted his trumpet, and the musicians from the school’s marching band launched into a jazzy rendition of “Happy Birthday,” while Kathleen Janatsch of Pacific Balloon Designs watched from the driveway, a big smile on her face.

The players followed with “When the Saints Go Marching In.”

Anais Baldwin anchored the piece on baritone sax; Ruth Garcia played flute; Storm Mertz, tenor saxophone; Ramiro Ramirez, trumpet; Molly Dunlop, cymbals; and Emily Meehan, clarinet.

“I was very surprised; I was hysterical,” Smith said, her eyes brimming. “This was special because it’s my 80th birthday.”

The surprise — the surreptitious work of her daughter, Melody Mann of Black Diamond, Wash., and granddaughter Athena Bradley of Lexington, Ky., — was actually Plan B.

In Plan A, Mann was going to surprise her mother at her birthday dinner by taking her order as a waitress in a local restaurant, but that would have required her to rent a car, drive down from Washington and hope that the shock wouldn’t be too much for her mother.

“I was afraid it would give her a heart attack,” Mann said. “It just did not work out. It was 1,077 miles from my house to her house, and that’s one way. It just wouldn’t work out.”

Since neither daughter nor granddaughter could make the trip, Mann began looking for the most memorable birthday surprise she could think of, and she came up with the idea of a marching band.

“It’s nothing we’ve ever seen or done, it’s just the wildest thing I could think of; I wanted it to be that special,” Mann said. “She’s just a great mother, the best mother. We love her so much. She’s the sweetest person in the universe. She my best friend.”

Marion Linton, Smith’s neighbor from across the street, came hurrying up the driveway to share her longtime friend’s moment. Linton admitted she had played a role in the “deception,” too — to make sure Smith was dressed when she answered the knock at the door.

As band members and the balloon lady made their way up the driveway, Linton said, she called and asked, “Are you dressed?”

Mann said she knew something was in the air, she just didn’t know it would be a driveway serenade.

“I knew I was going to get a gift, but who knew what?”