By Ollie Stone-Lee
Political reporter, BBC News website
"No matter what happens in the future, rock and roll will save the world," said The Who guitarist Pete Townshend.
Bob Geldof wants to turn up the heat on the G8 leaders
The Live 8 concert may not quite put his forecast to the test, but it once again raises the question of whether microphone diplomacy and a pair of wraparound sunglasses cuts any ice with world leaders.
The first Live Aid centred on fundraising in the wake of television pictures of African famine.
Twenty years on, the rock campaigners are more political. Geldof's "just give us your f-ing money" cry is aimed not at the public but at the leaders of the world's richest countries, the G8 group.
This change is probably not suprising, given that Geldof once told comedy writer Richard Curtis he had won more money for Africa from tea with French President Francois Mitterrand than he had in the whole of the Band Aid/Live Aid exercise.
That must have been a terrific brew, but 20 years on he is after something a bit more substantial than afternoon tea - he hopes the concerts will encourage politicians to back his cause, and thousands to march and protest outside the G8 summit if not.
Whatever the merits of the case, his fellow Irish singer, Bono, has admitted some people think the worst thing of all is a "rock star with a cause".
The U2 lead singer told delegates at last year's Labour conference: "Listen, I know what this looks like, rock star standing up here, shouting imperatives others have to fulfil.
"But that's what we do, rock stars. Rock stars get to wave flags, shout at the barricades, and escape to the South of France. We're unaccountable.
"We behave accordingly. But not you. You can't... See, we're actually counting on you."
Previous forays by stars wanting to mix music and politics have not always ended in harmony.
Sting's Rainforest Foundation may be credited with saving an area of Amazonian forest bigger than Belgium but it has not stopped him being derided by some critics for being a preachy hippy.
George Michael's satire may have lost US fans
George Michael's anti-Iraq war song Shoot the Dog , which accused Tony Blair of being George Bush's poodle, so angered Americans that the former Wham star moved out of the US for a time.
In last year's US Presidential elections, Bruce Springsteen teamed up with Dixie Chicks and REM in an attempt to convince undecided voters to reject George Bush.
It prompted Republican fans to chant: "Shut up and sing."
REM's singer Michael Stipe later said: "You can't expect pop musicians on a pop tour to swing a presidential election in a country the size of the United States...
"What that tour did was to galvanise the feeling of personal activism that has taken hold in the US."
Irish painter Kevin Sharkey, whose work has been bought by celebrities such as Sinead O'Connor, is worried rock star campaigns could actually damage Africa.
He told BBC News rock campaigners were "at best naive and at worst dangerous" as the continent needed more than sticking plaster.
"Rock singers and pop stars get used - their hands get shaken, it gives politicians an opportunity to use them to up the youth vote," he said, attacking Bush and Blair over Iraq.
The success of TV chef Jamie Oliver's campaign to improve school meals suggests celebrities can make a difference where they combine personal expertise with public support.
Geldof argues that Live 8 can turn up the heat on leaders in other countries where aid campaigns have been lower on the public agenda.
He also has the advantage of having been part of the detailed work of the Africa commission set up by Tony Blair.
He may be fed up being seen as "Mr Bloody Africa" but it is a tag which means he is generally viewed as more than just another meddling rock star.