Immediately after the success of the BBC Radio Ballads, Ewan MacColl set about the Herculean task of trying to drag British folk music into mainstream culture. Frustrated by the dreary amateurishness of folk song performance, he decided to establish his own centre of excellence to professionalise the art. He called it "The Critics Group".

MacColl tutored select artists "to sing folk songs the way they should be sung" and to think about the origins of what they were singing. He introduced Stanislavski technique and Laban theory into folk performance and explored style, content and delivery.

BBC producer Charles Parker recorded these sessions to aid group analysis. 40 years on, the tapes have come to light. For the first time, a clear sound picture can be constructed of this influential group in action. Former group members Peggy Seeger, Sandra Kerr, Frankie Armstrong, Richard Snell, Brian Pearson and Phil Colclough recount six frantic years of rehearsing, performing and criticising each other. They recall the powerful hold that Ewan MacColl exerted which was eventually to lead to the collapse of the group in acrimony and blame.

Presenter Martin Carthy MBE, now an elder statesman of the British folk music scene, shared many of McColl's ambitions but didn't join the group himself. He listens to the recordings and assesses the legacy of MacColl's controversial experiment.

Producers: Genevieve Tudor and Chris Eldon Lee

The tale of an unexpected encounter between 20th century legends - a meeting which created a new template for global celebrity.

February 1964: The Beatles fly into Miami, sparking Beatlemania as they prepare to perform on The Ed Sullivan Show.

Meanwhile in a low-rent Miami gym, the underdog Cassius Clay trains to fight reigning champion Sonny Liston for the world title. The pundits say Clay hasn't a hope. Quite unexpectedly, the paths of these legendary figures cross.

British photographer Harry Benson arranges for The Beatles to visit Cassius Clay in the gym. Clay picks up Ringo and swings him around the ring as if he's no heavier than a toddler, as the other band-members lie at his feet. Clay pretends to knock all four Beatles down with a single punch. The resulting images remain in the memory long after this brief encounter.

The Beatles triumph on TV. Cassius Clay amazes all the boxing writers by defeating Liston. They suddenly both find themselves on the cusp of a new kind of stardom - they're young, outspoken and able to capture the global imagination.

John Wilson reports from Miami on the background to this unique encounter, with the memories of three people who were there at the time: photographer Harry Benson, who was travelling with the Beatles, writer Robert Lipsyte, who was covering the fight for the New York Times as a rookie reporter, and fight doctor Ferdie Pacheco, then working at the gym in Miami. All witnessed the moment when Cassius met The Beatles. John also taps the memories of Paul McCartney.

Producer John Goudie.

Singer/songwriter Erykah Badu tells how the Black Power movement changed American music forever in the 1960s. From free jazz to the first stirrings of hip hop, this is a story of when the new music met the new politics. Amiri Baraka, Archie Shepp and the Last Poets' Abiodun Oyewole offer reflections on a turbulent time in American history. Contains repeated use of language which may offend.

Singer/songwriter Erykah Badu tells how the Black Power movement changed American music forever in the 1960s. From free jazz to the first stirrings of hip hop, this is a story of when the new music met the new politics. Amiri Baraka, Archie Shepp and the Last Poets' Abiodun Oyewole offer reflections on a turbulent time in American history. Contains repeated use of language which may offend.

The Canadian songwriter reflects on his musical career, with observations from Jennifer Warnes , who sang in his live band and recorded an album of his songs, and Suzanne Vega, who was moved by his music while a teenager.

Marc Riley presents the story of Kraftwerk, arguably one of the most influential bands of the 20th century and certainly one of the most enigmatic. Former Kraftwerk member Wolfgang Flür and fans including including Gary Numan, John Foxx, The Smiths’ Johnny Marr and writer Paul Morley offer their impressions of the band without whom modern music would sound very different. Part of Radio 4 on Music, re-releasing the best of Radio 4's music back catalogue.

Sean Street recalls the Radio Ballads, a series which heralded a completely new form of radio feature making which began in 1958. Mixing original voices and sounds with specially composed music, producer Charles Parker and folk singers Ewan MacColl and Peggy Seeger eloquently documented the lives of people who, up to that point, had rarely been heard on the BBC. Charles's daughter Sara recounts how the series began and its continuing influence on programme makers and listeners.

Benjamin Zephaniah reassesses dub poet Linton Kwesi Johnson's 1978 debut album. Dread Beat an' Blood expressed the black British experience as it had never been heard before. Using his trademark spoken word style set to an instrumental reggae beat, the record voiced the frustration of a generation. Linton discusses the issues he tackled on the record, such as police harassment, the National Front and the criminal justice system. Thirty years on, how much has changed?

Lynne Walker talks to the hugely influential American composer about the evolution of his music, his interest in African and Indonesian music and jazz.

Music critic Pete Paphides tells the story behind three 'follow-up' albums - from Dexys Midnight Runners, Fleetwood Mac and Suede - with tales of musical pressure, creative differences, personal politics and mixed results.

How many bands have found themselves with a massive and often unexpected hit album, only to struggle with the creation of their next opus? Sometimes the follow-up exceeds the first album, but often nerves kick in and bands are removed from the very stimulus that created their magic in the first place, finding themselves in a world of creative confusion, sycophants and accountants.

Pete Paphides talks to musicians, producers, and critics to explore the stories of follow-up albums with the same expert knowledge he brought to Lost Albums.

Programme 2: Fleetwood Mac - Tusk

How do you follow a record that sells 21 million copies worldwide and spends over 30 weeks at number one in the US album chart?

The answer is Tusk - the album Fleetwood Mac recorded in the wake of 1976's Rumours.

Despite joining the band just three years previously, this was the record that saw Lindsey Buckingham impose his will on Fleetwood Mac using the studio as a crucible in which he shovelled intra-band infidelities and his new-found love of punk.

In 1979 it was deemed a failure, nicknamed "Lindsey's folly" from industry insiders. After 35 years, it has been reappraised as their boldest, most forward-looking release, "a peerless piece of pop art", influencing Radiohead and REM.

Produced by Laura Parfitt