Early yesterday morning, as blossoming crocuses and daffodils were being covered with a mattress of spring snow, the stalwarts of Harvard Square's late night culture were running at full bore.

Although the late night scene at Kinko's, the Tasty and the handful of convenience stores in the area is obscured by the daily blizzard of academia and consumerism, it is the only culture available between the hours of 3 and 5 every morning.

The slick-looking granite building on Mt. Auburn Street that Kinko's occupies may be a text-book Boston office building, but when the late-night crowd takes over around 11 p.m. the innocent-looking copy center begins to change into club Kinko's.

Just after midnight copy expert Michael Poller switches from the classical and easy-listening favorites to what he calls the "more hard core" head-bangers of Offspring and Bush.

Smith says that he and his two colleagues rock through the wee hours of the morning until about 7:30 a.m., when the next shift comes in and turns the volume down a few notches.

A place for classic food and classic rock, the Tasty occupies its own niche in the music world. Yesterday morning a 4:30 a.m. patrons were sipping their coffee to Van Morrison's "Gloria" and various super-hits from the Allman Brothers.

According to the staff, however, the music choice is not as important as the Tasty's high-tech sound system, which can be operated by the proprietor as he stands be hind the grill.

"I'm pretty sure we're the only coffee shop in America with a discotheque sound system," said Rob Theil, who flips burgers, pours coffee and shoots the breeze with customers on most Tuesday mornings.

Unlike some of its fellow early-morning operations, the Tasty's late-night atmosphere benefits from its landmark status in the Reed Block building on John F. Kennedy Street.

yesterday morning the April Fool's crowd was reminiscing about a recent episode where, the customers all said, every member of the Harvard football team had to touch the diner's door naked.

Patrons were also amused several years ago on April Fool's Day when the alternative Boston radio station WFNX broadcast all day that the Nine Inch Nails had scheduled a show at the Tasty. Regulars got high quality entertainment for weeks afterward as suburban teeny-boppers came looking for tickets.

At store 24 on Mass. Ave., unlike the Tasty and Kinko's, hard-core music goes to max and the sound system doesn't quite meet professional standards.

"I have to listen to fuckin' culture club," said Brendan Burke, who works Tuesday mornings behind the register at Store 24.

"We used to have a radio [behind the counter] but customers complained," he said. "They would come in here and we'd have fuckin' Black Flag blasting with swears 'n' stuff."

But while many who burn the midnight oil try to add dance-club fever to pass the monotony of their work, the graveyard shift is not all about musical taste.