Because TV usually offers larger audiences and salaries than radio, series that excite listeners are rapidly offered to viewers. I've Never Seen Star Wars, in which stars try out activities they've previously avoided, is the latest, crossing from Radio 4 to BBC Four next Thursday. Such transfers often show their roots: the intense attention to voices in Little Britain results from creating characters who could orginally not be seen, as, more obviously, does Dead Ringers.

I've Never Seen Star Wars is a good example of a dual-use idea: Barry Cryer changing a nappy for the first time is a spectacle that works equally well heard or seen. Ironically, for a series with a sight-verb in its title, I've Never Seen Star Wars is a glimpse of the economic future of broadcasting: a series where it's irrelevant whether you see it or not.

Tribute is paid to a very different form of entertainment in Comedy Songs: The Pop Years. But what exactly, one of the first questions asks, is a comedy song?

"A song that makes you laugh," suggests Victoria Wood. She should know, having sung dozens in her breakthrough TV gig on consumer show, That's Life.

She's an original whose song, Let's Do It Again, is described as a mix of George Gershwin and Alan Bennett, as she celebrates "the absurdity of the mundane".

Who cannot warm to a song whose lyrics include the lines "Bend me over backwards on me Hostess trolley" and "Beat me on the bottom with a Woman's Weekly"? Eat your heart out, Andrew Lloyd Webber.

The history of comedy songs reflects the changing voice of comedy in general, from music hall songs, to Peter Kay's recent number one, as Geraldine with The Winner's Song.

Writer David Quantick traces the origins of the comedy song back to "some pillock in a jester's hat with a lute, singing about his genitals to the king, making it up as he went along".

One thing about comedy songs is that they may be irritating, but you can't stop singing them. The skiffle era gave birth to such memorable ditties as Does Your Chewing Gum Lose Its Flavour On The Bedpost Overnight? What sort of mind comes up with a lyric like that?

The birth of the singles chart in the early 1950s meant that comedy songs could make money. The Barron Knights and The Goons had hits. There were topical songs at the start of TV's That Was The Week That Was, and Benny Hill sang about Ernie, who drove the fastest milkcart in the west.

Many songs came from TV shows like The Two Ronnies, The Goodies (doing the funky gibbon) and It Ain't Half Hot Mum duo Don Estelle and Windsor Davies duetting on Whispering Grass.

Comedy songs gave hits to people who wouldn't normally expect to make the charts. Barry Cryer recalls having a number one in Finland 50 years ago with a cover version of Purple People Eater - which, on reflection, sounds like something you might find in Crooked House.

A new panel game, Act Your Age, ostensibly pitting comics from different generations against each other, sounded like a poor man's Mock the Week, with the six contestants, including Lucy Porter, Stephen K Amos and Barry Cryer, vying to come up with the funniest jokes or anecdotes. It wouldn't have mattered that chairman Simon Mayo's scoring was fashionably arbitrary if he'd made a wittier contribution, or helped the contestants out when they were floundering. Any panel game that is reduced to knock-knock jokes in its first outing is going to struggle to find an audience.

They act their age, but they're not funny

I can remember laughing only once, and even that was spitefully. Stephen K Amos, Lucy Porter, Barry Cryer and, bizarrely, Roy Walker had pitched up to pick up a cheque by not trying very hard.

One of the many great things about this venerable Radio 4 panel game is the chance to hear Barry Cryer's fruity chortle. If it were possible for a sound to qualify for 'national treasure' status, his contagious, wheezy wonder of the comedy world definitely would. It makes frequent outings in this marvellously nutty half-hour of fun. Part of BBC4's tribute to Humphrey Lyttelton, it gives us highlights from the ISIHAC stage show, filmed just a few weeks before his death in April. Tim Brooke-Taylor sings Girlfriend in a Coma to the tune of Tiptoe through the Tulips; a totally crackers 'Quiz among Quizzes' puts Anne Robinson firmly in her place; and the late, great Lyttelton dispenses a barrage of beautifully weighted put-downs. It's a fitting send-off for the affable gent who's left a Humph-shaped hole in comedy.

Recorded at the Lowry in April of this year, this is the only complete filmed version of the touring show of Humphrey Lyttelton's much loved Radio 4 panel game, I'm Sorry I Haven't A Clue. Sadly it was also the last as Lyttelton went into hospital 10 days later. The set-up is the same as a standard radio recording, and includes regular panellists Barry Cryer and Graeme Garden.

Barry Cryer: How will we ever get over the Humph?

He [Humphery Lyttleton] never swore - too much style for that. Well, hardly ever. The last show we ever did with him was on our live tour, in Harrogate, just a few weeks ago. We were all at the same hotel. At breakfast he had prunes. He took one bite, looked up from his bowl and said: 'How can you f*** up a prune?'