In the early 1970s, Laurie Anderson was a sculpture major at Columbia University. She made sculptures from newspaper and fiberglass, though the aesthetic at Columbia, as she put it, "was that sculpture should be a) heavy and b) made of steel. I didn't fit into this esthetic very well." In 1973 she met the New York composer Philip Glass and started sitting in on his rehearsals. Anderson played the violin herself, and under the influence of Glass and other musicians she began to gravitate toward performance and film. Since she never finished the soundtracks for her films in time for showings, she would stand in front of the film and tell the stories and provide the music live. This was the beginning of performance art, which she has since been credited with inventing. Violins became her favorite props: she sanded one, burned one, mounted a loudspeaker inside one, filled one with water, popped popcorn inside a tin one, and, in one of her most famous routines, played a violin - whose bridge had been replaced with a tape recorder head - with a bow whose hairs had been replaced with audiotape with words recorded on it. The latter trick gave her an interest in backwards speech, such as "god" being "dog" in reverse.

And so Anderson went on, like many Downtown Manhattan artists, making provocative little performance art pieces that only people in New York paid much attention to. In 1981, however, Anderson got the idea of writing a song with only two chords, based around an electronically repeating syllable: "ha." It was inspired by a recital she had heard by Black vocalist Charles Holland, whose career had been squelched for decades by racism in the classical music world. Holland had sung the aria "O Souverain" from Massenet's Le Cid, with words that ran: "O souverain, o juge, o père": "O Sovereign, O Judge, O Father." Anderson decided, in homage, to write her own version of the song, kind of a "cover," with her own translation of the words. With a $500 grant from the National Endowment for the Arts, Anderson put her resulting song, "O Superman," on a record on a small New York label. To her astonishment, the song hit number two on the pop charts in England.

So great was the demand for "O Superman" that Anderson was forced to sign a deal with a major record label, Warner Brothers, in order to supply it. And thus suddenly, in 1981, the boundary between the world of rock and the world of art music definitively broke down. During the 1980s, rock groups performed at classical spaces, classical composers performed at rock clubs, punk rockers wrote symphonies, and avant-garde musicians discovered the electric guitar. Categories became totally confused - often, so did listeners. Finally, opera composer Robert Ashley, whose operas often employ a pop beat, made a distinction: "If a piece of music is under three minutes long, it's rock. Over three minutes, it's classical."

Composers had secretly envied rock music since the 1960s. Classical musicians were slow to admit that the heavy physicality of rock appealed to them. But in 1966, conductor Leonard Bernstein famously confessed,

"...as of this writing, God forgive me, I have far more pleasure in following the musical adventures of Simon and Garfunkel or of The Association singing "Along Comes Mary" than I have in most of what is being written now by the whole community of "avant-garde" composers.... Pop music seems to be the only area where there is to be found unabashed vitality, the fun of invention, the feeling of fresh air. Everything else suddenly seems old-fashioned: electronic music, serialism, chance music - they have already acquired the musty odor of academicism."

Bernstein was hardly alone.

The advent of minimalism in the musics of Terry Riley, Steve Reich, and Philip Glass, with its simple harmonies and steady beat, seemed to be an admission in the 1960s that classical music needed to loosen up and give audiences the opportunity to tap their feet again. Meanwhile, a few rock musicians were listening to minimalism and harboring their own lust for the vast length of minimalist works. Most famously, John Cale worked with minimalist composer La Monte Young during the day and with his own group the Velvet Underground at night. In "The Black Angel's Death Song" from The Velvet Underground and Nico, the famous Verve disc with Andy Warhol's banana painting on the cover, the viola drone and static texture are legacies of Young's influence.

Likewise, other rockers and bands got into the act. David Bowie and Brian Eno heard Philip Glass's Music with Changing Parts in England in 1971, and began incorporating drones and repetition in their rock albums. Passages of composed, quasi-minimalist patterns began appearing in the early '70s music of groups like Yes, Genesis, and Pink Floyd. Frank Zappa incorporated wild improvisation and dissonant gestures into his music, and in addition wrote liner notes that sparked interest in Varese, Webern, Feldman. Even the Beatles got into the act: their public enthusiasm (and that of The Who as well) for Stockhausen caused a temporary run on that composer's recordings, and under the influence of Yoko Ono - an avant-garde composer herself who had been associated with John Cage and La Monte Young - they appropriated tape-splicing and loop techniques in 1968 for the tape collage Revolution No. 9 on their "White Album."

Like Oscar Wilde, musicians of the '70s could resist everything except temptation. At last, in 1977, Rhys Chatham - the music curator at the Kitchen, New York's prime space for avant-garde music - created a furor by inviting experimental rock bands to come and perform. Chatham, who was a minimalist composer himself, decided he could make minimalist music with classical guitars just as well as with anything else. Also in 1977 he wrote a piece called Guitar Trio, consisting entirely of rhythmically played overtones of a single pitch.

Meanwhile, as Chatham was approaching rock from the classical world, another figure was passing in the opposite direction. Glenn Branca had begun as a theater person who, like many nonmusicians of the late 1970s, thought starting a rock band sounded like too much fun to pass up. With guitarist Jeffrey Lohn he founded a punk band called Theoretical Girls. "Jeff and I," he would later say, "got into an incredible competition as to who could make the most outrageous, completely ridiculous piece. I "plugged a recording of white noise into the p.a. - a wall of white noise. Then we played a jagged version of "You Really Got Me" by the Kinks underneath it. In one piece I wrote, each musician played at a different tempo. I played a fast Chuck Berry thing. The bass player did a sort of reggae pattern, at not only a different tempo, but a different feel entirely. The drummer was instructed to play something completely off with everything he heard. It sounded fabulous."

Working briefly with Chatham, however, and also under the influence of the Polish composer Krzysztof Penderecki, Branca became fascinated with the possibilities of continuous, slowly changing electric guitar textures. By 1981 he was writing full-length symphonies for masses of electric guitars, and by 1983 in his Symphony No. 3, subtitled "Gloria," he was tuning his guitars to pure overtones. It's true that the sheer loudness of Branca's guitar symphonies tends to overwhelm all other considerations. But it's equally true that his rhythmicized, repetitive conflicts between harmonies preserve the heart of the symphonic tradition, especially if you compare them with Branca's 19th-century symphonic hero Anton Bruckner.

The rivalry between Rhys Chatham and Glenn Branca has resulted in ever larger works, in a furious crescendo of one-upmanship. Chatham, in 1987, went over the top by writing a symphony for 100 electric guitars called An Angel Moves Too Fast to See. Because of the difficulties of finding 100 electric guitarists in any one location who can all read music, the piece is divided notationally into tiers of guitarists, some of whom need to read notes, and others who only need to count. As Chatham admits, "A hundred guitars can't really be louder than three," but must of the interest of An Angel is spatial, hearing huge sonorities bouncing back and forth among different locations in his huge ensemble. Eventually, Branca responded with his own symphony for 100 guitars, called Hallucination City. It was premiered in July of 2001, in front of the World Trade Center.

Other refugees from the avant-garde, tired of its sterility and waning relevance, started adding a rock beat to their acts. One of the most frightening of these was Diamanda Galas, an amazing singer with a range of three and a half octaves. Galas started out singing music of the European avant-garde, but in the early 1980s started making her own hair-raising works for voice and electronics, with titles such as Wild Women with Steak Knives.

In 1984 Galas began a trilogy based on Edgar Allen Poe's "Masque of the Red Death," intending it as an allegory about AIDS. Soon it became clear that mere allegory was too timid for the crisis at hand; instead, she would attack religious hypocrisy at its roots. Providing her own text dotted with passages from the Bible and religious liturgy, she created an evening-long stage work that assaulted bigotry directly, a counterattack against religion for its condemnation of homosexual AIDS victims. The 1986 death from AIDS of Galas's brother Philip, a well-known playwright and performance artist, added fuel to the fire. Galas's The Masque of the Red Death is one of the most powerful music theater pieces of the 1980s, divided into three parts with provocative titles - The Divine Punishment, Saint of the Pit, and You Must Be Certain of the Devil. To drive home her jeremiad to the people who most needed to hear it, Galas subverted rock and even country and western idioms.

Another important member of an older generation, also known for dealing with sex and violence in his music, became something of an underground rock star. Robert Ashley had been a member of the lively ONCE group in Ann Arbor in the 1960s, best known for a piece called Wolfman in which he would scream into a microphone with the amplifiers at maximum volume to produce ear-splitting feedback. In 1978 he began a new career as a composer of text-based theatrical works, beginning with Perfect Lives. "These are stories bout the Corn Belt, and the people in it... or on it," croons Ashley at the beginning of each episode. Perfect Lives is, in a roundabout way, the story of two musicians, Raoul and Buddy, who come to a small Midwestern town to play at the Perfect Lives Lounge. There they fall in with two locals, Isolde and her brother Donnie, captain of the football team. The four form a plan to steal all the money from the local bank for one day and then return it. Buddy's dogs create a diversion at the bank, and they take the money off with friends Ed and Gwyn, who are eloping. Isolde's father, the sheriff, figures out the plot, but too late to stop it.

Ashley, a highly collaborative composer, writes the texts for his operas himself, and works out the rhythmic and harmonic structure. Many of the details depend on people he works with regularly: "Blue" Gene Tyranny, the phenomenally versatile piano player who plays Buddy; Peter Gordon, a multiple-threat musician known for his rock group the Love of Life Orchestra; rock singer Jill Kroesen; baritone Thomas Buckner; percussionist and performance artist David Van Tieghem; and several others. In addition, Ashley's operas are not at all operas in the conventional, European sense: they're made for television, with video as a primary component. "I put my pieces in television format," he has said,

"because I believe that's really the only possibility for music. I hate to say that. But I don't believe that this recent fashion of American composers trying to imitate stage opera from Europe means anything.... We don't have any tradition. If you've never been to the Paris Opera, never been to La Scala, never been to the Met more than once, we're talking primitivism. How can you write the pieces if you've never been there? It's like Eskimos playing baseball."

Nevertheless, Ashley has rarely been able to get his operas produced for television, and many of them have existed only in stage format. Starting with Perfect Lives, he has written over a dozen operas, some spinning off from the same characters, including Improvement: Don Leaves Linda, El Aficionado, Now Eleanor's Idea, and Dust. Little acknowledged by the operatic or classical music world, Robert Ashley is nevertheless the most important underground opera composer of the late 20th century, one of American music's great mavericks.

The mixture of genres so rampant in the 1980s sorted itself out again in the clearer 1990s. Once again, pop music was pop music, classical was classical. Nevertheless, composers born in the 1950s had grown up with rock, and were incurably infected by it. The physical energy of pop was bound to make its way into their music, particularly in the context of a style that became known in New York circles as totalism. Totalism suggested having your cake and eating it too - having enough rhythmic energy to appeal to pop fans, yet also enough complexity to satisfy the musical connoisseur. In the 1990s, a steady beat was essential for musical hipness. Around that beat, though, you might have different tempos at the same time, 12-tone melodies, harmonies diffracted as through a prism, sudden tempo changes like gear shifts. Totalism was a music of simple harmonies, like minimalism, but with a rhythmic complexity that rivaled jazz and African music.

Some totalist composers have aimed for a pop-music surface, with rhythmic intricacy in the background. One of the smoothest of these is Mikel Rouse, a New Yorker who has produced several operas, music theater works, and even films. Born in rural Missouri in 1957, Rouse studied African rhythm from A. M. Jones' seminal book Studies in African Music, and also studied Schillinger technique, a mathematical approach to rhythm and pitch developed in the 1940s by Joseph Schillinger and popular at the time with Tin Pan Alley songwriters. Rouse's early music reflects these influences, written for rock quartet with overlapping rhythmic layers spreading out in hypnotic patterns.

Fronting his own rock group in the '80s, Rouse turned to music theater in the '90s with a one-man opera called Failing Kansas. Based on the same murder as Truman Capote's docunovel In Cold Blood, Failing Kansas abstracts texts from the original court case into what Rouse calls "a 75-minute pop song." Letters by the murderers Dick Hickok and Perry Smith are spoken in rhythm, underlaid by a plethora of contrasting and simultaneous rhythmic patterns. From Failing Kansas Rouse progressed to a much larger work called Dennis Cleveland: an opera in the form of a talk show. Rouse himself plays the talk show host, Dennis Cleveland. Some of the singers are hidden in the audience as audience members, and only reveal themselves when Rouse comes up and sticks a microphone in their faces. Despite a tremendous rhythmic complexity in the background, Dennis Cleveland has brought delighted audience responses in performances around the world, including last year at Lincoln Center.

Where Rouse brings a classical type of structuring to the materials of pop music, others infuse classical instruments with the energy of rock - such as Michael Gordon, one of the curators of New York's popular Bang on a Can festival. Gordon started out in the 1980s with his own ensemble modestly named the Michael Gordon Philharmonic. From the very beginning, in pieces like Thou Shalt!/Thou Shalt Not!, Gordon favored a hard-hitting beat derived from Led Zeppelin and other '70s rock. You'll hear in this example, though, the way he tends to shift between slower and faster beats, a gear-shifting effect which is part of his musical personality. In later works, Gordon trained his ensemble to switch instantly between complexly related rhythms, a common characteristic of totalist music. Pieces like his Yo Shakespeare require the ensemble to nod their heads to a common beat, even when no one is playing on the beat.

Like many composers from Manhattan's Downtown scene, Gordon started out writing for an ensemble of his own, in the tradition of Steve Reich and Philip Glass., and then began to get larger commissions as his fame grew. Even when he writes for string orchestra, though, as in his hour-long work Weather, the energy is not that of a mid-century avant gardist, but a rock keyboardist gone legit.

It was not that classical audiences were looking for rock-inspired pieces, or that pop audiences wanted more serious fare than they were used to listening to. The audiences remained quite separate, safely kept that way by a recording industry that could make more money marketing to well-categorized audiences. But the young composers were tired of compartmentalizing their intellectual skills and their emotions. They played in garage bands as teenagers, got classically trained in college, and they wanted to be able to use all their skills in one piece. Many of them secretly envied rock stars, and their titles referred to rock music. David Lang wrote an homage to Jim Hendricks called Are You Experienced?, and Michael Gordon's I Buried Paul harked back to a rumor that those words could be found when an old Beatles album was played backwards. Their teachers, typically, wrote dry, intellectual music that rarely got played, while secretly enjoying jazz standards at home. The young composers found this hypocritical, and "No more guilty pleasures" became their motto. And then they had to find, or else create, an audience that wanted an in-between music, that wanted the formal intricacy and seriousness of classical music combined with the physical energy of pop.

The problem was to get that physical energy in a music that was notated and did not depend on the performer's sexual charisma. Julia Wolfe, another of the Bang on a Can curators, tried to bridge this gap in her work Lick by applying minimalist additive processes to riffs inspired by Led Zeppelin. Los Angeles composer Art Jarvinen, one of the most sonically inventive of the current generation of composers, has articulated his pop rhythms using mousetraps, pencil sharpeners, and spray cans, as in his Egyptian Two-Step. Eve Beglarian started out a composer of complex serial music as a student at Princeton and Columbia, but inevitably migrated toward minimalism and Downtown performance art. While many rock-inspired composers face the charge that their rock music references are always ten years out of date, Beglarian is always in pace with the latest trends. Her work frequently involves her own voice and is always thoughtful, even when describing the seedier side of New York over a pop beat.

David Garland, a regular on New York's Downtown scene and announcer for WNYC, is a cross between pop songwriter and electronic sampling musician. Some of his songs, like "Happy Ending," hark back to rock music's innocent era, while still taking advantage of new sampling technology. Garland can make pop music accompanying himself on toy piano or even just hitting two pieces of styrofoam together; or he can make an entire song from sound effects recorded and stored in a keyboard.

In fact, one of the most interesting twists in recent music is that rock need no longer be made by guys jumping around stage with guitars; it can be made by someone quietly staring into a computer. California composer Carl Stone makes almost all his music by sampling sounds he finds in the world - recording them and storing them - and then transforming them rhythmically with delays, loops, and echoes. Stone spends much of each year in Japan, and in his composition Kamiya Bar - Stone's pieces often have strange titles because they're all named after restaurants, especially Asian ones - in Kamiya Bar he takes the environmental sounds of a busy Japanese street and rhythmicizes them into a rock beat. Perhaps nothing could be more emblematic of the changes going on in the new generation's music than Stone's Hop Ken, which takes a recording of a classical warhorse, Mussorgsky's Pictures at an Exhibition, and, using the computer, jumbles and reassembles it into a pop beat.

"The authentic poet," wrote Wordsworth, "must create the taste by which he is to be enjoyed." Is there a taste yet for a music in-between pop and classical? This is the great question for the younger generation of American mavericks: is there an audience out there, or will one grow up, who will appreciate the seriousness and scope of classical music when couched in the sounds of the American pop vernacular? If we may go back to words used near the beginning of this series, let's quote early 20th-century American composer Henry Gilbert: "American music... has this problem to face: that it can only become ultimately distinctive by leaving the paths of imitation, and that by leaving the paths of imitation it must temporarily sacrifice both immediate success and the respect... of both public and academician."

The American maverick composers have certainly not chased after immediate success, nor have they cared for the respect of the academy. Instead, they have clung to a stubborn faith that music need not be comparmentalized, that it can bring together heart, brain, and body. They have believed that music can be intelligent, brilliantly structured, deeply felt, and also set your foot tapping, all at once. They have believed that the vernacular musics of America constitute a rich soil from which a distinctly American classical music can grow. They have believed that any true music is the voice of a people, and that American music should not be a transplant from Europe, but a home-grown product voicing our national passions and aspirations. They have believed all this in the hope that an audience will arise to hear them.

Wordsworth's statement suggests that the music comes first, and then the audience. The music is here.