The lights in the stadium dim as the drumbeat of the band sends the crowd into a frenzy. A voice screams out, ''open the pit!'' and an empty circle materialises in front of the stage.
A whirlpool of bodies forms around its rim and people begin to plunge into the centre.
The formation, known as a ''death circle'', is a new form of extreme moshing being embraced by fans but raising safety concerns among crowd management authorities.
Seven years after 16-year-old Jessica Michalik died in a crowd surge at the Big Day Out festival in Sydney, moshing the mass movement of spectators to live music is alive and well.
''(Moshing activities) happen all over the place, at any and every venue with a reasonably sized crowd,'' says Jon Corbishley, risk and safety manager at Australian Concert and Entertainment Security. The ''wall of death'' is another moshing formation, in which the crowd separates into two facing sides, leaving a gap of at least 10 metres, and then violently rams into each other.
''We make the wall of death because it is a thrill,'' says 16-year-old concertgoer Lucas Fabi, from the inner Sydney suburb of Pyrmont. ''The adrenaline you've got in your body ... it just bursts out while you're moshing. It's just fun.''
Formations like this are hard to control at large concerts, says Philip Eggeling, operations manager of Playbill Venues.
''It's really hard to control the crowd when they're running around in circles,'' he says.
However, the extent of moshing depends on the type of concert.
''You wouldn't get it at a James Blunt concert,'', says Neil Stalker, operations manager at Sydney Entertainment Centre.
Scott McLennan, editor of the Adelaide street press magazine Rip It Up, says moshing is seen by many young people as something of a rite of passage.
''From teen experience, emerging from a mosh pit with a black eye, a fat lip and a cut head was not so much a painful experience as a badge of honour,'' he says.
Seventeen-year-old Eden Vander Kallen, of Abbotsford in Sydney, appears to bear this out. ''I've been in the wall of death, I've got a scar on my leg to prove it. I'm telling you, it's the shit,'' he says.
But participants insist they don't set out to cause harm. They describe moshing as a release of tension and an expression of belonging and unity, as well as a sign of appreciation for the music.
''Real moshing is the release of expression through physical means,'' Croydon teenager Jaxon Brown says. ''It should be how you feel expressed through your body, with no brain to filter (it).
''Pretty much anything is OK as long as it is indirect and there is unity.''
Enthusiasts says friendships and camaraderie are also fostered in the mosh pit. ''You know you meet someone cool when you hit them in the pit and they say 'good hit'.
''I have made a few friends like that,'' Vander Kallen says.
But getting involuntarily swept into a circular stampede of bodies isn't everyone's idea of fun.
''If you're in the wrong spot at the wrong time you have no choice whether you want to do it or not. That's what scares me the most,'' says Silvia Pinneri, 18, of Denistone.
Not participating in moshing can even be more dangerous than joining in, McLennan says.
''Unfortunately at the periphery of these pits there's always people who merely want to watch the show and don't want to partake in the frenetic and physical displays of the ... pit,'' he says. ''For them the situation can be antisocial and dangerous, since they're stationary obstacles that are often struck by errant moshers.''
Some bands actively encourage extreme moshing behaviour, says Tim Cashmere, senior music writer at the online magazine Undercover.com.au.
''I've lost count of the amount of bands I've seen demanding a ... circle pit ... of an audience that is only too happy to oblige,'' he says. Other bands have encouraged new variations on moshing formations, such as the ''wall of carnage'' and the ''tsunami of death''.
Dr Mick Upton, head of the Centre for Crowd Safety at Bucks New University in Britain, found in a recently updated report that 25people died ''at the front of the stage'' in concerts around the world between 1974 and 2002.
The figures include nine concertgoers who were crushed to death at a Pearl Jam concert in Denmark in 2000. Under recent legislative changes, Australian patrons who mosh do so at their own risk and venues cannot be held liable for injuries. However, since Michalik's death in 2001, new safety measures have been put in place to prevent massive crowd surges and dangerous behaviour.
Many concert venues use a ''D Barricade'' to split the mosh pit into front and back. The Entertainment Centre's Neil Stalker says the venue also videotapes the mosh pit, runs risk assessments for each show and notifies other venues where the band will perform of crowd behaviour.
Many concert venues also require ''high risk'' bands to agree not to encourage reckless behaviour, Acer Arena security supervisor Eddie Silvio says.
''(They) are asked to sign a waiver if they have a history for enticing dangerous crowed behaviour brought under notice from our risk assessment process,'' he says. ''It basically means if they entice the crowd to do any dangerous behaviour or anything contrary to what they have signed, we will pull the plug, we won't allow them to carry on.''
Moshers say they follow their own pit etiquette, such as immediately helping anyone who has fallen down, removing spike bands before entering the pit and not kicking, punching, groping or sexually assaulting anyone.
But concertgoers who breach safety rules find themselves turfed out, says Silvio. ''Anyone that's being absolutely stupid and going totally crazy with disregard for anyone else's safety, under our duty of care, is removed from the venue straight away,'' he says. ''Until someone gets severely injured or, even worse, dies, these kids won't really understand the implications of their behaviour.''
AAP