Satchmo Blows Up The World Penny von Eschen Harvard University Press, pounds 19.95/pounds 18.95 (free p&p) from 0870 079 8897
PENNY VON ESCHEN takes her title from an article in Drum magazine celebrating the African tour which Louis Armstrong and his All Stars made at the height of the Cold War in 1956. He had been sent by CBS television, which wanted to film his return to his roots, but when the US government saw the ecstatic local response, they couldn't wait to send him back as their cultural ambassador. Neither could the soft drinks companies which plastered Lagos and Accra with the slogan: "You like Satchmo. Pepsi brings you Satchmo. Therefore you like Pepsi."

The real motor in this story is the US State Department, which in the mid-Fifties made the export of jazz its pet project. As von Eschen points out, this was extraordinary, given that jazz was still regarded by conservative Americans as a degenerate art fuelled by sex and drugs, and that its leading lights were black. While America was in the throes of a last-ditch battle between segregationists and the civil-rights movement, her cultural agencies were flourishing black jazz musicians as the country's badge of acceptability.

Presidents Eisenhower, Johnson, and Nixon desperately needed that badge, Johnson comically so. After he gave mortal offence to the jazz-loving king of Thailand by sitting cross-legged with his feet pointing towards the monarch's face, Stan Getz was sent east to smooth things over. More seriously, jazz ambassadors were despatched whenever the US had an image problem, or wherever the battle for oil, cobalt, uranium or tin looked like being lost to the Soviets. As covert US operations in countries bordering Vietnam grew in intensity, so did the jazz onslaught, helped by spin from the Voice of America.

Willis Conover, who fronted its music broadcasts, opined that "jazz is a musical reflection of the way things happen in America ... People in other countries can feel this element of freedom. They love jazz because they love freedom." Some of the ambassadors agreed. Benny Goodman - who jammed with the delighted Thai king - was declaring as early as 1956 that racism had been routed in America, and that jazz had played its part.

Others remained obdurate. Satchmo blackmailed Eisenhower into a reluctant crackdown on racism in Alabama by threatening to tour no more.

This book abounds in piquant moments where artists went off-message. Duke Ellington caused a furore by parading with his unmarried companion in Baghdad in 1963. The scandal was only defused thanks to Kennedy's assassination, the next day.

Von Eschen's prose may occasionally get clogged, but this book fascinates on many levels. Whether for juicy anecdotes or a potted history of jazz in Soviet Russia, where the Americans were amazed by the expertise of fans, this is where to look.