It is 21 years since John, Paul, George and Ringo, barely out of their teens and wholesome-looking, stepped nervously into Studio Two of the EMI Records building on London's Abbey Road and started packaging the sounds that soon made them arguably the most famous musical practitioners of modern times.

In all, the Beatles recorded 188 of their 210 songs on these unimposing premises and in 1969, they went outside to the crosswalk to be photographed for the cover of the "Abbey Road" album. Therefore, in the hierarchy of shrines to the Beatles in Britain--and with the passing of time there are an increasing number--Studio Two is right near the top.

"It was my stupid idea to open this place to the public," Ken Townsend, EMI's general manager, told one of the scores of reporters attracted by the notion of seeing the historic site. "We've been astounded by the interest," he said.

Beginning this week and for the rest of the summer, EMI has put on display the original recording equipment, instruments and other memorabilia from that '60s heyday. The 50-year-old building in a quiet residential neighborhood is still very much in use. In the fall, after the tourists are gone, Studio Two will get an overhaul.

In the meantime, to accompany a specially produced videofilm of the group in action, two previously unreleased Beatles' songs were retrieved from archival obscurity and outakes of many of their most famous numbers were blended into an interesting sound track--a project akin to compiling sketches by a Renaissance master.

EMI's motives in this undertaking are not wholly magnanimous. The entry fee for the three showings a day is about $7 a ticket and a souvenir stand aims to wring further cash from the all-too-eager-to-pay fans. Lest anyone get the bright idea of pirating the new Beatles songs, visitors are searched and tape recorders removed.

Yet there is an earnestly reverential quality to the exhibition. Somber classical music is played as people file into a high-ceilinged chamber with subdued lighting, decorated with Beatles pictures and the recording paraphernalia that guarantees this room is the real article. Promised refreshments turn out to be orangeade and cookies.

Most of the crowd, it would appear, were born after the Beatles hit the big time. Anneli Langhans, a 19-year-old from West Germany, said she finds nothing "old-fashioned" about the music and her friend nodded in accord. In the next row, a 17-year-old British girl said her older brother had introduced her to the Beatles years ago. The group, she said, remains a part of her life.

Yet there is something dated about it all. The equipment seems especially primitive. There are devices that record at two tracks, for instance, compared with the 48 tracks that are used in today's big production numbers. Each take had to be restarted from the beginning if there was a mistake. As a result, it took two weeks to finish "Love Me Do" in 1962.

Early shots and sounds of the group show how quickly they grew up in the face of the popular hysteria they aroused. Within five years, the videotapes show, the soft-edged boyishness of the first sessions was replaced by something harder.

The two previously unknown songs are "Move Over 109," apparently written by Lennon and McCartney, and "Leave My Kitten Alone," a number first performed by a singer named Little Willie John. It isn't clear why neither was released and there doesn't seem to be any reason why they shouldn't be now. The narrator of the video asserts that rumors of vast quantities of still unreleased Beatles material are wrong.

Opening the EMI studio is the latest development in a trend toward rendering Beatles history into (money-making) museums. In Liverpool, local officials are unabashedly hoping to capitalize on their best-known native sons to round up some badly needed tourism.

The Cavern Club, where the group got its performing start, was covered over by a parking lot several years ago. But a nearby building has been turned into a "semi-replica" and various events are staged throughout the year, featuring, among others, ex-Cavern Club disc jockeys. In late August, a three-day Beatles "extravaganza" is scheduled in a large downtown hotel.

Last summer the city council renamed streets so that more of them would be indentifiable from Beatle song titles. A statue of the group is also in the works. While the three remaining Beatles, Paul McCartney, George Harrison and Ringo Starr, are plainly doing nothing to discourage these moves, there's no sign they are behind them either.

"The Beatles haven't made a single contribution to the city," Sir Trevor Jones, a leading Liverpool politician, said. Nor have they lent their support to the EMI show by providing any new interviews for the videotape. In that sense, everything the group had to offer, they gave a long time ago.