IT IS 3am in a dank, sweaty studio in south London. Ear-splitting basslines pound from the sound system. Some of the young crowd gently bob along. Others are drinking, chatting or lurking in dark corners. Then, suddenly, the music changes. A throbbing pulse gives way to a clattering rhythm. Where there were 130 beats per minute, there are now 170. Where the mood was meditative, it is now maniacal. Within seconds the place is jumping.

This music is called “jungle”. Some of the people in the club were probably not alive when it was created. Certainly few would have been old enough to experience it in its heyday. These young revellers have an ear for the next big thing; they find trips down musical memory lane tiresome. Yet nothing seems to animate them like these tracks from almost 20 years ago.

To understand jungle's roots, you must travel yet further back in time. On March 11th 1970 Richard L. Spencer, tenor saxophonist and lead singer for a short-lived Washington, DC, soul act called the Winstons, was awarded a Grammy for “Color Him Father”, a sentimental ode to a devoted stepfather released by the band the year before. The record sold well, but unlike some of his fellow winners that day, who included Aretha Franklin, Joni Mitchell and Johnny Cash, Mr Spencer was not destined for musical canonisation; the Winstons had already split up and later that year he quit the music business. The song, too, has largely been forgotten.

The same is not true for “Amen, Brother”, the B-side to “Color Him Father”. It is not immediately apparent why this should be. The two-and-a-half-minute instrumental, a funk update of an old gospel standard, is sprightly enough; the casual listener might be diverted by the energetic horn line. But there is little to distinguish it from hundreds of similar records released around the same time. The band recorded it quickly, says Mr Spencer; they needed a B-side and didn't have any other songs.

Seven seconds of this track were enough to guarantee its immortality. One minute and 26 seconds in, the horns, organ and bass drop out, leaving the drummer, Gregory Coleman, to pound away alone for four bars. For two bars he maintains his previous beat; in the third he delays a snare hit, agitating the groove slightly; and in the fourth he leaves the first beat empty, following up with a brief syncopated pattern that culminates in an unexpectedly early cymbal crash, heralding the band's re-entry.

“Amen, Brother” lay dormant for almost two decades. But in 1986, as the nascent hip-hop scene in New York was entering the musical mainstream, the song cropped up on the first volume of “Ultimate Breaks and Beats”, a compilation of tracks with “clean”, drums-only segments. DJs and producers using turntables had long used breaks from old funk tracks as backing material for rappers; the compilation made their lives easier. Combined with the sampler, a new piece of digital hardware that recorded snippets of sound for deployment in other contexts, it allowed producers to create extended loops over which rappers could perform.

The first hip-hop producers to use what became known as the “Amen break” did so with no great ambition. Many looped only the first two, “straight” bars of the four-bar break. Amen was simply one of many tools in the producer's kitbag.

When jungle was massive

A journey across the Atlantic liberated the break. In the early 1990s British producers in the rapidly evolving dance-music scene were seeking new sources of inspiration. The repetitive grooves of American house and techno provided one; the reggae sound systems operated by Anglo-Jamaicans were another. But more than anything it was the sampler that galvanised these producers. Their tracks developed a distinct identity, supported by a complex infrastructure of record shops, pirate radio stations, nightclubs and raves: they sped up, acquiring an urgent, almost manic quality, relying increasingly on the creative possibilities for rhythmic experimentation opened up by the sampled breakbeat.

The producers of what was coming to be known as jungle found a number of old breakbeats that suited their needs. As these beats began to crop up in more and more records—they were, in the parlance, “rinsed”—fans began to recognise them, and to compare the ways in which producers had manipulated them to generate distinct effects.

Chief among these breaks was Amen, which many producers first heard on “King of the Beats”, a six-minute instrumental collage of hip-hop beats and other samples released by Mantronix, a New York producer, in 1988. The track made extensive use of the Amen break, but in a fresh way: segments from the loop were chopped up, layered and processed so that the drums became central to the track rather than simply a rhythmic bedding.

Like a virus, once the Amen break had taken hold among jungle producers it began to propagate, and to mutate. It was used on hundreds, possibly thousands of records (some claim that “Amen, Brother” is the most sampled track in the history of music). For a time anyone trying to build a name in the scene had to turn their hand to Amen. “The musicians chose to limit themselves in order to express creativity within boundaries,” says Simon Reynolds, a journalist and author who chronicled the rise of jungle in Britain.

As the music grew more sophisticated (and the technology more powerful), the manipulation of the break grew wilder; producers engaged in a sort of Amen arms race. “It was a battle to see who could do more with it,” says Karl Francis, who, recording as Dillinja, was one of the more radical Amen experimentalists. “But the tunes still had to work in the club. Sometimes I made tracks that went too far and people would just stand on the dance floor looking confused.” Listeners grew attuned to the break's sonic elements; before long the merest hint of Amen was enough to drive crowds into a frenzy. Coleman's seven-second break had entered the collective aural unconscious of a generation of young Britons.

A Proustian snare drum

Why was Amen so popular? One answer is that it fulfilled a need: easy to sample and manipulate, it offered producers a straightforward way into jungle. Many amateur producers, including this correspondent, have been surprised to discover how easy it is to make the junglist equivalent of instant noodles by sampling, looping and speeding up the break. Eventually Amen acquired critical mass; producers used it because everyone else did.

But Amen also has certain sonic qualities that set it aside from its rivals. Rather than keeping time with a hi-hat, Coleman uses the loose sound of the ride cymbal, filling out the aural space. And the recording has a “crunch” to it, says Tom Skinner, a London-based session drummer: “That quality is appealing to beatmakers.” The pitched tone of the snare drum is particularly distinctive; as any junglist will tell you, a snare can be as evocative as a smell.

The displaced snare of the third bar and the syncopated last bar became signature elements of many Amen tracks. At 170 beats per minute the jumpiness of these parts of the break becomes urgent. Mr Reynolds talks about the “panic rush” of the break at this tempo, the “state of emergency” it created among clubbers. Mr Skinner draws attention to the way deft producers would emulate drummers' tricks in their manipulation of the break, creating “ghost notes”—rhythmic shuffles of sound that help the beat swing. Others introduced hyperactive snare rushes or stop-start mini-loops, and deployed the cymbal crash to signify not the beat's conclusion but rather its ongoing pressure. “It's language that existed before, but you had never heard a drummer playing quite like that,” says Mr Skinner. Like all musical movements rooted in a particular period, jungle slipped first into a decadent phase, and then became a nostalgia piece. The futuristic frenzy became routine; beats became metallic and funkless; the sampled break was often replaced by the drum machine. Elsewhere the lilt of the accelerated breakbeat, its harsher edges smoothed away, proved attractive to makers of commercials and composers of television-title tunes. Many Americans first encountered Amen like this; it crops up, for example, in the theme of the popular cartoon series “Futurama”.

Before long the merest hint of Amen was enough to drive crowds into a frenzy

But Amen never went away. Some keepers of the flame continued to use it to signal their devotion to the good old days, or to conclude what they considered to be unfinished business. Guitar bands occupying different musical universes from jungle producers, such as Oasis, found uses for this most versatile of breaks.

Today, when the generation that first exploited Amen is nudging middle age, a younger wave of musicians has begun to uncover new meanings in this loop. Some use it to express a stern oath of fealty to a movement they were too young to experience. In the tracks of others you hear a plaintive yearning for a simpler time, when producers could use breakbeats without feeling that they were freighted with meaning. A sample that once encapsulated dreams of the future now struggles to escape its past.

“A lot of young people are nostalgic for things they weren't there for,” says Micachu, a 24-year-old London-based musician. For her own Amen project, with Pete Wareham, a jazz saxophonist, she ruled that the only permissible sounds were Mr Wareham's sax and her treatments of the break: “Every producer should give their take on the Amen break. It's like a composer doing a chorale.” (Mr Wareham says that he had not heard of the Amen break by name before, but that when he sought it out “the last 20 years flashed before my eyes.”)

If the Amen break belongs to anyone, the 1990s generation who performed their extraordinary acts of alchemy on it would seem to have a strong claim. But in a much more tangible sense, the break, along with the rest of “Amen, Brother”, belongs to Mr Spencer, who retains the copyright to the Winstons' back catalogue. The band's former front-man says that neither he nor Coleman, who he says died in poverty in 2006, received any royalties from the extensive reuse of Amen. Mr Spencer says he only became aware of its rebirth in 1996, when he was phoned by a British music executive seeking the master tape of “Amen, Brother”.

Whose break is this?

Mr Spencer is not interested in the digital age and its remix culture. He dismisses the music spawned by the track as “plagiarism” and “bullshit”, considering it another chapter in the plundering of African-American cultural patrimony. “[Coleman's] heart and soul went into that drum break,” he says. “Now these guys copy and paste it and make millions.”

It is a tricky area, acknowledges Mr Reynolds. He notes that had Mr Spencer received a fraction of what he considers to be his dues he could have retired early and put his children through college. On the other hand, he and Coleman have achieved a sort of immortality: “It's a bit like the man who goes to the sperm bank and unknowingly sires hundreds of children.” Mr Skinner agrees that it is a shame the original musicians earned nothing from the reuse of their work, but says, “you don't want a world where sampling can't happen.”

The legal infrastructure surrounding sampling has become more robust. Yet even if the legion of small-time producers who were using sampled breaks 15-20 years ago could somehow have been identified and challenged, it is not as if Mr Spencer would have received anything; jungle would have taken a different form—or perhaps simply been crushed. That would have counted as one of the music world's minor tragedies.

The best Amen tracks discussed: economist.com/node/21540676