The week in radio: Hey Mr Taxman sing a song for me (otherwise I'll throw you overboard)

Ghosts R5 The Speech Makers R4 The Beatles - the Last Show WS Something Understood R4

My father's uncle threw a tax inspector into Sydney harbour and sailed away, never to be seen again. His descendants call him Poor Tom but there's always been a certain dashing glamour about him: tax inspectors, after all, have been reviled since Biblical times. Yet, although the thesaurus equates evasion with avoidance, it is legal to avoid tax, illegal to evade it. After hearing Ghosts (R5), it seems thoroughly immoral, too : Poor Tom becomes Disgraceful Tom.

Lesley Curwen's excellent investigation into these shadowy figures, clinging like mud to the grubby hem of society, began with a repellent villain. Mike is a motorbike dispatch rider, but he has made a tidy cash income selling pornographic books, ice-cream and hot-dogs, never declaring a penny of it. He prefers not to appear on any official records and his philosophy is to look after number one. He's doing well: he has private health insurance and a private pension. He would never give to the homeless, he said primly, as the money would be wasted on drink.

People like him account (or don't) for about pounds 85 billion of lost national income. You could wish that Curwen had asked him about all the other services he uses - dustmen, education, police, defence, etc - for which the rest of us pay, but she probably didn't want to spend too much time with him. Instead, she was off for a chat with a prostitute called Siren who described herself as an artist in oral sex. Siren sees her body as capital equipment that needs expenditure to keep it alluring but tax inspectors don't agree, so she's another ghost. Listening to all this, you get the nagging feeling that comes when drug-dealers are interviewed: should they be allowed to get away with such smug parades of law-breaking, or shouldn't R5 pass their files straight to the Inland Revenue?

An academic was called in; he said that these people, along with queuebargers and benefit fraudsters, belong to a particular personality type known, unsurprisingly, as "the self-serving". In the second programme, this afternoon, the taxmen give their side of the story.

There was another interview, with an illegal immigrant from Slovakia who works on building sites. Far from being defiant, he was so nervous of detection that he had asked for his voice to be disguised. It sounded like one of those scribbled-out photographs used for similar purposes in newspapers. The individual voice is as revealing, and as vital to identity, as the eyes, as we heard in The Speech-Makers (R4).

This was an odd little series, spread over four afternoons. There was a charlatan called Jo. He had been married twice and fathered children but was thinking of becoming a woman so had been referred to the Gender Identity Clinic at Charing Cross Hospital and given the female pronoun. Now they were working on making "her" sound like a woman. Jo said that female nose-blowing was deeply unsatisfactory and that the voice dropped "like knicker-elastic" when using the telephone.

All went well for a while, then a reversion became apparent. The speech therapist expressed doubts as to Jo's commitment to transexuality. Jo agreed, adding that the limelight of changing sex would dim when femaleness was achieved. Convincing women are, kind of, less visible. We left Jo wearing the trousers and moved to Margaret. She had suffered a laryngectomy, which made her side of the interview tricky to grasp, lip-reading not being very effective on radio. But Margaret was a feisty star. The microphone was there to capture her first words with a new, husky but definitely still Brummy voice. She asked for a cup of tea. She didn't add "and make it snappy," but it was clearly only a matter of moments.

Thirty years ago, a technician called Keith was sent off to Oxford Street to buy a pair of tights. When he said that he didn't care what size they were, he realised that he was less likely to be thought a cross-dresser than a bank robber. In fact, the tights were to protect a microphone from the wind howling around a rooftop where a memorable concert was about to happen. The Beatles Show - The Last Show (WS) was a terrific programme. People who had been filing clerks and office juniors at the time were unearthed and invited to recall the extraordinary day in January 1969 when the world's most famous group clambered onto the roof of their office building in Savile Row and started to sing. As the traffic stopped and the West End became immobilised, surrounding windows were thrown up, firedoors opened and neighbouring rooftops filled with an impromptu, ecstatic audience.

It was curiously touching. The experience of those ordinary office workers had been the epitome of serendipity, giving them dining-out material for the rest of their lives. Besides, the band itself was on the point of disintegration. The gang of Liverpool boys had grown up and were developing individual ambitions. As one of them said, "we couldn't go on being clean little mop-tops all our lives." The concert ended when Stephen King, the Chief Accountant of the Royal Bank of Scotland (and probably an ex school prefect) summoned the reluctant cops. Negotiations allowed one more song, "Get Back," with extempore lyrics, interrupted by laughter. "You been playin' on the roof again ... get back where you belong." I found myself wondering whether Stephen King had subsequently adopted a new, even less wholesome career.

Time to revert to the blessed calm of a Sunday morning, when Something Understood (R4) regularly occupies half a million minds (even more if you include the evening repeat). This anthology is a quiet success story, giving people what they seem to want. It is highly eclectic, spiritual rather than religious, and seriously undidactic. Denis Tuohy introduced last Sunday's edition, which was about the quest for enlightenment that defies verbal definition. Undaunted, he had a good try, citing the words of St John of the Cross, Krishnamurti, Voltaire, R. S. Thomas, Arthur Miller, Thomas Malory and David Constantine - a pretty broad cross-section. Routine drudgery must not be allowed to sabotage our dreams, said Tuohy: all too often, we don't know when we're well off. Relevant music gives the bemused and sleepy listener a chance to think about that. Last Sunday's playlist included

"Ballad of El Dorado", Bernstein;

"16 Tons" Tennessee Ernie Ford;

"When I Survey the Wondrous Cross" Watts;

"Spirit Garden" Takemitsu;

"I Still Haven't Found What I'm Looking For"

U2.