The man who's rescoring the British musical

Forget the Beatles. Forget the Rolling Stones. The English tunesmith who is currently packing 'em in on both sides of the Atlantic is an Oxford-accented composer who works with biblical characters, South American rulers, and cats.

He is Andrew Lloyd Webber - a slight, doe-eyed songwriter who is one of Britain's hottest musical properties, Boy George notwithstanding. ''Transatlantic king of popular musical theater,'' trumpeted The Times of London when Mr. Webber's latest hit, ''Starlight Express,'' opened there this spring.

His success with award-winning musicals - including ''Jesus Christ Superstar, '' ''Evita,'' and ''Cats'' - is no small feat. In an artistic genre whose standards have traditionally been set by such American composers as Richard Rodgers and Stephen Sondheim, Webber has elevated the English musical to new heights.

And in a country whose theatrical tradition has been split between an impeccable reputation for serious drama and a less noble history of vaudevillian British music hall, he has brought an all-American style of song-and-dance theater to audiences weaned on Shakespeare - while expanding the audience for British musical theater in both the United States and the United Kingdom.

''Practically every theater up and down England now considers it an important thing to do - to take on a mainstream musical,'' said the composer during an interview here on one of his frequent US visits. ''That is a completely new perception.''

Deena Rosenburg, chairman of the musical-theater program at New York University's Tisch School of Arts, agrees: ''For the first time ever, London is exporting musicals when they've traditionally imported American shows. That's a very new thing.''

The evidence seems to be everywhere.

When ''Evita,'' Webber's unconventional work about Argentine First Lady Eva Peron, surpassed fellow Briton Lionel Bart's ''Oliver'' as England's longest-running musical and went on to snare seven Tony Awards in New York, critics hailed it as the coming of age of British musical theater. And last year Webber achieved what no other British composer ever had - sextuple billing, with three shows running simultaneously in both New York and London. Today, at least six shows in the United Kingdom and the United States still throb to Webber scores.

For the composer, such success ironically had to do with his not becoming a rock star.

''I had the luck to be very interested in musicals when a lot of other people weren't,'' Webber says, reaching for the tea trolley here in his hotel suite. ''After Elvis (Presley) and the Beatles, younger people weren't really interested in staying with musical theater. Even in America, the great age of musicals was prior to 1964. When pop (music) broke out, people saw that as a shortcut (to success). Only those really interested in theater stayed with it.''

Unlike composers in the US, who indigenously developed the American musical from a tonally diverse culture that included jazz, gospel, and big-band sounds, British songwriters had no such rich melodic history. But Webber's imitative skills and gift for musical parody allowed him to create his splashy, stylized productions, unique subject matter, and scores that are a melodic pastiche of pop, rock, and quasi-opera.

''When 'Cats' (the musical based on lyrics by poet T. S. Eliot) opened, everyone was skeptical,'' he says. ''At the time it was really breaking a considerable amount of new ground - it was the first musical that worked outside a conventional proscenium stage. . . . The shows that are durable over the years are the ones that broke some kind of new ground in a number of different areas - 'West Side Story,' 'My Fair Lady,' even 'South Pacific.' . . . In my own work I've noticed the more adventurous the works have been, the more successful they've been.''

While some observers have criticized the composer's flair for the unusual as being based on style rather than substance, others insist that Webber is simply bringing musical theater in line with contemporary culture.

''Popular music and theater used to be synonymous in the '30s and '40s,'' says New York University's Deena Rosenburg. ''Webber's scores come the closest to bridging that gap. By taking sounds that have mass appeal and harnessing them to the theater, he is widening the audience for musicals.''

Webber's techniques are also considered progressive, expanding the limits of musical theater. Along with fellow composers Sondheim (''Sweeney Todd'') and Michael Bennett (''A Chorus Line''), Webber is credited with creating the ''bookless musical'' - one that uses nonstop song and dance with little dialogue. It's a form that divides critics, and it's one that Webber defends.

''I've always found the arrival of the book has a tendency to get in the way, '' Webber says. ''One of the joys of writing contemporary musical scores is that the composer is really the person whose boat it is. The actual music stands on its own right and less as a series of songs.''

Nonetheless, some observers have charged that Webber's scores are derivative, produce few hit singles, and are characterized by bombast and pretentious epic proportions. ''Plotless extravaganza . . . an allegorical spectacle aimed at all age groups,'' wrote music critic Stephen Holden about ''Cats'' in the New York Times.

Other critics have questioned the number of architectural renovations necessary for mounting Webber's larger-than-life shows - nearly half the seating capacity of London's Apollo Victoria Theatre was ripped out for the ''Starlight Express'' railroad-track set. While some observers insist that much of the composer's success is due to his talented directors - including Hal Prince (''Evita'') and the Royal Shakespeare Company artistic director, Trevor Nunn (''Cats'' and ''Starlight Express'') - other experts privately question whether such highly stylized productions can maintain their relevance.

Webber is undeterred. ''With the exception of Sondheim, there has been no vast risk-taking'' until recently, he says - although he adds that the spiraling costs of Broadway musicals and a lack of qualified song-and-dance performers in London have been additional impediments. But now, the composer says, the tempo is picking up. Greater artistic cross-fertilization is occurring between London and New York, the caliber of British performers has improved, and Britain has established its first-ever musical-theater tradition.

Born to a musical family - his father was a composer and conductor, and his brother is a classical cellist - Webber was composing early on for a toy theater and memorizing ''all the albums of hit American shows backwards.'' But it wasn't until he attended Oxford University that he met his first collaborator, lyricist Tim Rice, and began the series of Webber-Rice ''rock opera'' hits.

When the composer was not yet 20, he and Rice wrote ''Joseph and the Amazing Technicolor Dreamcoat,'' an Old Testament narrative set to a musical crazy quilt. Although originally commissioned for a children's concert, ''Joseph'' eventually earned multiple Tony Award nominations, encouraging the young team to write its next blockbuster, ''Jesus Christ Superstar.'' Although both it and the subsequent ''Evita'' were originally produced as record albums - no producers could be found for apparently risky musicals about Jesus Christ and Eva Peron - both shows went on to international stardom.

''One shouldn't put things into categories,'' the composer insists. ''In the theater there is room for anything that is in the end profoundly theatrical.''