THE world of opera is in for something of a shock. Those arch villains of musical mockery, Kit and The Widow are vamping it up in The Fat Lady Sings.

Eschewing their more usual erudite Flanders and Swann personae, the demented duo will be taking great works and great singers to task in what they describe as, "a swab test on the tonsils of opera".

They have cajoled talented mezzo-soprano Melanie Marshall into joining them at the Yvonne Arnaud Theatre, Guildford, from August 24-26.

She may well regret that decision given the satirical and lunatic reputation of Kit Hesketh-Harvey and Richard Sisson.

The venue is a bonus for The Widow. Not only is it the first theatre he ever attended as a child, but he says: "Arnaud audiences are some of the most responsive and theatrically literate."

Both Cambridge graduates, Kit and Richard were involved in the famous Footlights but their paths later diverged.

Kit pursued a career as a writer and translator but Richard returned to his student job as a waiter at Claridges. A fluke brought him into the world of club cabaret in company with Kit a year after graduation.

It was an alien field for them both. "We were counter-trendy. We weren't political and had to learn how to do it simply by doing it," said Richard.

The Widow (a nickname from his student days when he played Widow Begbick in the Rise and Fall of the City of Mahagonny) hates pretension and this latest collaboration aims to deflate operatic pomposity.

"We can match the Three Tenors for volume but there will be no throat spraying or waving large handkerchiefs during the performance, thank you. We will also stray into the strange world of the 'lavender' tenors - counter-tenors such as Alfred Deller.

"Kit can," The Widow admits grudgingly, "sing a bit". In fact he was a choral scholar at Clare College.

"We're really lucky to have Melanie Marshall joining us. She has a voice that suits classics, jazz and comedy. I once heard her sing songs from Porgy and Bess on a tropical beach and it was stunning."

Less stunning for Richard is rehearsal. "Kit and I will do anything to avoid it. One thing I hate when I perform as a piano soloist at the Wigmore Hall is that I have to keep practising."

The opera show is something of a departure for this 25-year partnership.

"It will show a slightly different side to us; it's a bit of an adventure."

In fact the two are opera fans and visitors to Glyndebourne. Kit is currently translating A Turk in Algiers from Italian to English.

As well as taking the grand out of opera, the duo will stray into the world of operetta, music by Sondheim, Joyce Grenfell, Coward, Flanders and Swann (of course) and perhaps even Fascinating Aida.

"With all the fuss about rebuilding the Royal Opera House and the controversy over inequality in funding for the arts, opera is a very current topic.

"It seems that every English composer has the desire to write an opera. It's very difficult. It really is the equivalent of writing six symphonies and you have to have a dramatic sense. It's a big financial risk too."

Richard is no slouch himself when it comes to composing. He has been residing in Luton this year as part of the Year of the Artist. Here has been teaching classical music and was commissioned to write for a local music society.

He also wrote the music for Alan Bennett's stage version of The Lady in the Van, has been involved with the Choir of the Year competition and composed the music for Nicholas Write's Cressida at the Albery Theatre.

"If you are a music lover," says Richard, "come along to hear Melanie, even if you have to grit your teeth while we're on!"

Sandy Baker