Watch a tour of U2's 'claw' stage with tour architect Mark Fisher
U2's latest tour rolls into the UK this weekend, when Bono's band bring their groundbreaking "claw" stage to Wembley.
The group perform in the round, with speakers, lights and a cylindrical screen suspended above them. They say it lets them get closer to fans, gives the crowd a better view and allows them to squeeze more people in.
From the Beatles to Bono, via Led Zeppelin and Live Aid, outdoor gigs have become hi-tech, theatrical spectacles, with spectacular ticket prices to match. Here are some of the landmarks in the evolution of stadium rock.
THE BEATLES - SHEA STADIUM, NEW YORK, 15 August 1965
Beatlemania was the catalyst for the birth of stadium rock
With Beatlemania rampant, the Fab Four made history as the first band to perform a stadium gig.
The screams from the 55,000-strong crowd were so loud that the band were barely audible in the home of the New York Mets baseball team. The group played on a stage in the centre of the stadium as 2,000 security personnel battled to keep crazed fans off the field.
The set-up was primitive, with the sound fed through the public address system. "You've got 55,000-60,000 kids, screaming their lungs out, and actually sounding louder than the band," says Mark Cunningham, editor of live music magazine Total Production International. "But the kids didn't really go to hear the music."
LED ZEPPELIN - KNEBWORTH, 4 & 11 August 1979
The heavy rockers had played one of the first stadium tours in the US in 1973. Six years later, they returned to the UK to play two shows in the grounds of Knebworth House.
Between 200,000-400,000 people saw them play what would be their last full UK shows. Among other things, the shows were notable for their use of big screen technology.
"I was there," says Mr Cunningham. "It was quite astounding because you had this screen at the back of the stage. It was this huge landscape. From far away, you could see Robert Plant singing. It was something I don't think anyone had seen before."
GENESIS - ABACAB TOUR, 1981
In a bullring in Barcelona, Genesis fans saw the first moving stage lights - something that would become common at concerts everywhere.
The inventors of the Vari-Lite had demonstrated their gadget to Tony Banks, Phil Collins and Mike Rutherford during rehearsals, and the band liked it so much that they invested in the new company.
"Up until that point, all lights were static," Mr Cunningham says. "And then suddenly you had this show where the beams were moving, sweeping. We take that for granted now. I can't overstate how influential that was."
LIVE AID - WEMBLEY STADIUM, LONDON & JFK STADIUM, PHILADELPHIA, 13 July 1985
Live Aid brought together the world's biggest rock and pop stars
Billed as the biggest rock event the world would ever see, Live Aid was a transatlantic 16-hour show, broadcast live on TV and radio to more than 1.5 billion people in 160 countries.
Paul McCartney, Bob Dylan, U2, Madonna, Queen, David Bowie, Led Zeppelin and Mick Jagger were among the artists who appeared to raise money for African famine relief.
"The thing that always amazes me is that they organised that concert at Wembley without e-mail or a fax machine," Mr Cunningham says. "They had one telephone in the production office and if anyone else wanted to make a call, they had to run to a phone box."
DAVID BOWIE - GLASS SPIDER TOUR, 1987
Bowie pioneered the art of performance over several world tours, combining rock with theatre, costume and choreography.
The Glass Spider tour, which began at the Stadion Feijenoord, Rotterdam, and was seen by three million people, was the culmination of his elaborate efforts.
U2's long-time stage designer Willie Williams says: "That has become the blueprint for Madonna, Janet Jackson, Britney, Kylie...
"There will be one set of costumes and they will do a few songs, then there will be another big scene change and move on to the next thing. Bowie crossing rock 'n' roll with Broadway was where that began."
ROLLING STONES - STEEL WHEELS TOUR, 1989/90
The Steel Wheels tour, first seen in Philadelphia, was on a new scale, with a bigger, more extravagant stage and higher ticket prices than ever before.
The band performed in front of a futuristic eight-storey metallic structure that was partly inspired by Blade Runner. The tour broke box office records, taking almost $100m in the US and Canada.
Mr Williams says: "That was a monumental stage, and with that came a new financial model. Until then, rock shows were cheap entertainment. It was like going to the cinema. Steel Wheels was the first expensive rock ticket, and they pumped the extra revenue into building this absolutely colossal stage."
U2 - ZOO TV TOUR, 1992/93
U2 made full use of new technology for their multi-sensory extravaganza
U2 took the rock spectacle to a new level with Zoo TV, which began in Florida in 1992.
Video became central to the experience, with three dozen screens bombarding the audience with images and messages, and Bono using a remote control to flick through live satellite TV channels.
The singer also put on costumes and make-up to adopt a number of larger-than-life characters, while 11 Trabant cars hung above the stage, with spotlights in their headlights.
"Our contribution was to run with the multimedia ideas-based shows, but combine that with the scale required to fill a stadium," Mr Williams says. "Zoo TV rewrote the book in terms of how video was presented in a rock show."
U2 are playing in London, Glasgow, Sheffield and Cardiff between 14-22 August.
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