Labels don't fit Glenn Branca's rare brand of music

The first time I heard a performance by Glenn Branca and friends, I didn't know what hit me. The piece was called ''The Ascension,'' and it was like nothing I'd ever heard - dense, loud, complex, all-enveloping.

The first time Branca heard his own theories put into practice, a few years ago, he was similarly surprised. He had been playing rock with his band, the Theoretical Girls, and mulling over musical ideas - especially the notion of creating what he calls a ''standing wave'' of continuously strong, pungent, tightly packed sound.

One day he gathered six guitar players together, tuning their strings to his own specifications. ''I thought if I used enough guitars, I could not only set up a standing wave, but work within it,'' he told me recently in his modest lower-Manhattan digs. The challenge was to generate a field of ''white noise,'' then break it down into a harmonic texture ''while keeping its ambiguous quality.''

The experiment worked, though the sound was richer and stranger than expected. ''The theories were all well and good,'' Branca now says. ''But when we actually tried it, we were amazed.'' Encouraged, he tried to figure out what was creating the sound, then carry it a step further in each new piece. Like a sonic scientist, he concocted further experiments to identify the ingredients that gave his ''standing waves'' their power.

Years later, Branca is still enthusistic about his rare brand of music. And audiences are beginning to share the feeling. Performances have been well received in venues ranging from a Hudson River beach to the prestigious Brooklyn Academy of Music, where his Third Symphony bowed last fall. His music accompanies dances performed by the Alvin Ailey American Dance Theater and Twyla Tharp's troupe.

Several pieces are available on recordings, some from his own Neutral Records label. A collaboration with ''performance artist'' Eric Bogosian will open this fall at the Provincetown Playhouse in Manhattan.

This growing popularity doesn't mean Branca's music is easy. It's aggressive, sometimes abrasive, often ear-splittingly loud. Instruments may include a platoon of guitars. Or an oil drum whopped with a stick. Or large pieces of metal flung about the floor. Or devices invented by Branca, enabling players to strike many guitar strings at once. The sheer presence of the sound is so important that records are only a partial reflection of a performance.

''People have trouble labeling my music,'' Branca says, ''and I encourage that difficulty. Labels help to a point, but they limit how far your mind will go.

''I'd like to keep people off balance enough so their minds stay open. If they open themselves, anyone can relate to what I do. My music is about everybody's lives. It wants to make a positive statement and contribution.''

Odd as they sometimes are, though, each aspect of a Branca piece marks a careful step in the evolution of the ''standing wave'' and its many offshoots.

How did Branca's explorations begin? For years he created unusual ''musical theater pieces,'' often using found objects for instruments. Later he formed a rock band, but moved away from convention, indulging his fascination with John Cage and other classical renegades.

Branca found himself less interested in song structure than in ''emotional structure.'' He determined ''to remove the things that usually entertain people in music, and bring it all down to one person trying to communicate with another.''

The result, he admits, was often ''a kind of emotional confusion.'' But that's all right, he says. ''I wanted to create a very immediate situation for myself and the audience. One way was to use this harsh, extreme sound. I was concerned less with the sound than with the emotional impact. And there seemed to be plenty of that.''

New developments came so fast he had trouble keeping up with his own ideas. His First Symphony used quarter-tone intervals (between the notes of the familiar Western scale) and guitars with plain metal wires as strings. The next symphony moved away from ''emotional structure'' and rhythm, showing a new interest in harmonic complexity.

Most recently, Branca has studied - and fallen in love with - the basic musical concept of the ''harmonic series,'' which roots musical sound in physics and mathematics. ''Overtones and harmonics, and the philosophical ideas behind them, are dominating my whole thinking,'' he says eagerly. ''They have a diabolical symmetry - absurdly simple, yet reflecting the beautiful and amazing complexity of nature. They make you respect nature in a new way, and seriously consider the idea of a superior intelligence. . . .

Branca stands amazed that the harmonic series is so universal - ''it relates to quantum physics and the shape of a seashell'' - but has been considered of more theoretical than practical value in music. He's bent on changing this. ''I didn't write half of my last symphony,'' he says. ''Chords and progressions were determined by the harmonic series. If you call this excessive, all right. But I can't remember when I've felt involved in something so exciting and real. Let's make music from the music of nature!''

Branca's next step is to spread the word about these matters; the album of his Third Symphony will include a booklet on them. He cares a lot about audiences - ''they're almost a part of the music,'' he says - and wants to make his work as accessible as possible. Yet intellectual understanding means less to him than a ''visceral, emotional'' response from his listeners.

''A lot of people think of art as pretentious, weird, limp-wristed, not for them. But good art is none of those things! Except'' - and a mischievous smile cracks his youngish, grizzled face - ''maybe pretentious, just a little. And we're working on that. . . .''