The camera pans across the crowded restaurant and focuses on the elegantly dressed woman staring mournfully at her male companion. She’s armed – with eyedrops. “Stand by, we’ve got tears going in,” someone shouts, and with our heroine’s ducts sufficiently diluted, the music swells up around us. She rises to her feet, and rage, hurt and bitterness mingle in a lacerating passage of Baroque blub-bing. I know it can’t be real – the video screens, film crew and eyedrops tell that story – but it doesn’t mean I don’t want to look away, or at least stop that spotlight from beaming intrusively into a tear-drenched face.

This is my first exposure to The Full Monteverdi – though it won’t yet tally with anyone else’s. In its 76 performances, scattered over three years and more than a few countries, the show presented by the British vocal group I Fagiolini has always been a live experience. You, the audience, simply take your seat in a café or restaurant, and the six singers and six actors of the show play out the train-wrecks of their relationships among you with Monteverdi’s music. You wouldn’t even know they were sitting next to you until the gentleman at the table by the window suddenly informs his dining partner in a ringing tenor that whenever she weeps and sighs, “those tears are my blood”.

Thankfully, what has captivated all those audiences around the world (and won I Fagiolini a well-deserved award from the Royal Philharmonic Society) is being captured for posterity, as a TV film and DVD to be aired and released in the autumn following on from the final live performance next week at LSO St Luke’s in London and in the Lincoln Centre in New York. That’s why I’ve found myself in a curious sham-café somewhere near the Bristol ring road, constructed specifically for the filming of The Full Monteverdi, and learning from the group’s charismatic founder and director, Robert Hollingworth, exactly why the show struck such a chord when it was first unveiled in summer 2004 at the Cheltenham Festival.

“Most people never get to be that close to a performer when they’re really letting off steam,” he says. “But getting someone so close that they can feel the physical energy of the performer means they involve themselves emotionally in the subject matter in a way that they simply wouldn’t otherwise when listening to madrigals.”

There comes a tricky word – at least for British audiences. Say “Madrigal”, and as Hollingworth gloomily acknowledges, “it’s nymphs and shepherds, the whole Blackadder thing, and ladies’ choruses singing fa-la-la on a hillock somewhere.” But Monteverdi’s madrigals (he wrote nine books in all, and The Full Monteverdi is a complete performance of the fourth tome) conjure up an entirely different sound world. “You could say they’re operatic,” observes Hollingworth, “but that’s actually anachronistic because operas written at that time didn’t have anything like this layer of passion in them.”

Monteverdi’s Fourth Book of Madrigals isn’t, of course, actually about six singers telling six actors that they’re breaking up with them: the poetry is loftier than that. But according to John la Bouchardière, the man who devised the original stage concept, and who is directing the film adaptation, it isn’t too great a leap. “It’s a poet saying, ‘I love you, don’t leave me’ repeated by five voices at a time.”

The problem was finding a dramatic context in which the repetition would make sense. “I binned the idea for a while,” admits la Bouchardière, “but then one day, in a restaurant in London, I suddenly noticed that there was a couple on my right having a bad time, and then a couple on my left having a bad time. And I realised that we do say ‘I love you/ don’t leave me’ at the same time – we just don’t share it.” Adding the audience as the unprepared eavesdroppers gave the conceit its potency. “If people thought it was basically a concert that could just consume and spectate, then they weren’t involved,” says Hollingworth. “But when they didn’t know what the hell was happening – when it was ending, how far it was going to go, whether there was going to be violence, whether there was going to be sex, because there is an erotic madrigal in the piece, then they’re out of control and they’re really involved.”

Different audiences have reacted differently to the challenge of The Full Monteverdi. Typically, the British tend to politely avert their eyes from the nearest warring couple and focus on a performer elsewhere. A Dutch man once created mayhem by laughing throughout the first 15 minutes (“presumably out of embarrassment,” says Hollingworth) until his wife told him to shut up.

The other dangers of the live show have hinged around the scene-setting: in order to maintain the illusion, the singers and actors take their seats like any other punter, and sit in character before beginning the show. In Jerusalem, one indignant woman refused to give up the seat she had reserved for her husband, and when informed by the hapless singer that he needed it to perform, berated him for spoiling the surprise.

Whether the film version can hit the same targets, no one is entirely certain. It expands the scenario to include the back stories of each couple’s relationship, taking them outside the fateful restaurant and into hotel rooms and street scenes. The next morning – “a postcoital nightmare”, la Bouchardière calls it – is also dramatised. “And we can get close-ups and direct the viewer’s eye in a way that you can’t in the live show,” says Hollingworth.

The film and final performances also mark a poignant farewell from I Fagiolini to The Full Monteverdi, and – for most – a goodbye to the six actors playing the silent lovers. That is, except for one couple, the mezzo-soprano Clare Wilkinson and actor Mark Denham, who took advantage of the two and a half years on the road to form a more lingering attachment. “Yes,” quips Hollingworth, “and now they break up every night.”

I Fagiolini performs The Full Monteverdi at LSO St Luke’s, London EC1 on Monday (020-7638 8891). The film will be aired on Sky Arts HD and S4C in the autumn. For more details visit www.ifagiolini.com

Explore Music

• CD Reviews

• Live Reviews

Editor's choice

• Here comes summer: our cultural must-sees
• Friends reunited: Sex and the City
• New country for old men