RADIO / And the bands played on: Natasha Walter on Woodstock, Cambodia and evangelists of the air

History can repeat itself in more than one way. In Getting Back to the Garden, a celebration of Woodstock's 25th anniversary (Radio 2, Saturday), we saw that it often starts off as farce. Getting Back to the Garden made perfect radio, because in a way Woodstock only existed in the myths woven by music and shared memories. The bands played, and participants in the original Woodstock remembered the mud, the crowds, the joy, the nudity, the mud, the idealism, the music and the mud.

Some were not so impressed. The Who went on at 4am on that fateful Saturday night, and played till dawn. As Pete Townshend put it: 'I looked over the horizon, there was this amazing light, and I thought, bloody hell, good person on the lights today.' Their arrival wasn't so auspicious: 'My experience of Woodstock was absolutely appalling. I thought it was disgusting, hypocritical. We were dumped out of the car into about six feet of mud. All I got was all these Americans telling me that this was the beginning of a new life.' Their manager demanded their money before the group played a note. There wasn't any cash in the field, but one of the organisers woke up the local bank manager and helicoptered him over to the night safe to get some cheques. Peace and love, indeed.

But most people's memories were rose tinted: 'It was probably the closest to heaven I'll ever get.' The idealism began to grate; if they had credited themselves with inventing rave culture, fair enough, but the presenter seemed to see Woodstock as inspiring some pretty far-flung struggles. 'I saw the same chilling recognition of history being made in the faces of the kids at Tiananmen Square and on top of the Berlin Wall.' Still, the uncertain, inarticulate voices of today's would-be Woodstocks provided nothing but a tragic coda to the sweet excitement of the original participants, still vibrant after 25 years.

John Pilger went back to Phnom Penh in Grand Tour (Radio 4, Wednesday) and saw history repeating itself in more sinister ways. Original broadcasts from the Sixties to the Eighties were intertwined with readings from Pilger's books Heroes and Distant Voices and up-to- date commentary. Pilger has laboured to keep alive the memory of what the Khmer Rouge did in their Maoist or, as he insisted, fascist, state, where there were 'no families, no love, no holidays, no songs', and nearly a third of the country met their deaths.

It's one moral case that's always seemed open and shut. But Pilger reminded us that if it hadn't been for the recent participation of the United States and the UN in a peace plan that put the Khmer Rouge in a central role, the Khmer Rouge could never have returned to the strong position it occupies today. Now, it poses a continued threat to the fragile peace of Cambodia, controlling nearly a quarter of the country, its legitimacy accepted by the States and its camps supplied by Western relief organisations.

In the most telling image drawn by Pilger, he recounted Prince Sihanouk meeting the head of the UN mission and the UN military commander at a parade to celebrate the success of the peace deal. Beside them, as guest of honour, was Pol Pot's right-hand man.

Garrison Keillor made a striking case for deregulated radio in his programme Radio Preachers (Radio 4, Wednesday). He argued that a system that keeps all the whooping, eccentric gospel radios of the Bible- belt alive is 'not a homogeniser, it's an equaliser. A microphone makes the little person bigger and the big person smaller.' Certainly his tour round the hellfire and brimstone stations of the American South made sparkling listening; here were preachers who shouted 'Ha' at the end of every phrase; preachers who wanted you to touch the radio and feel the spirit; 86-year-old singing and dancing preachers. Keillor was right, it's a rich and funny medium, worth keeping alive so long as you don't listen too carefully to the messages: 'No compromise. You have tuned to the programme where we breed intolerance of the liberal, pagan elite.'