The West End/Broadway musical is alive and well, raking in millions with its blend of light music, song and dance routines and not-too-taxing drama. But its spiritual ancestor, the operetta, is an unfashionable beast. Offenbach's weighty Tales of Hoffmann gets produced many times more often than his most popular operetta (Orpheus in the Underworld) and the others languish far behind, which makes Jeremy Sams's new production and translation of La Périchole for Garsington Opera into an unusual event.

The music of La Périchole is pure escapist delight. What amazes is Offenbach's ability to switch styles and excel in all of them. His baseline is a stated aim to outdo the Strauss family at their own game: the score bubbles over with waltzes and other dances of the period, interspersed with feel-good romantic ballads. But Offenbach closes the first act with a big ensemble number which could have been written by Mozart. In Act III, our hero Piquillo languishes in a prison cell from which he is about to be rescued by his adoring wife. As we discover shortly afterwards, Fidelio it ain't, but the music is a perfect pastiche of the high romantic style. And the Peruvian setting provides the opportunity for a slew of Spanish dances every bit as beguiling as those in Carmen. It's extraordinarily winsome music, and conductor David Parry kept everything light, upbeat and fun. Balance was perfect - impressively so for a semi-outdoor venue like Garsington Opera's pavilion.

Offenbach's satire still punches its weight. You need to be armed with a couple of historical facts provided in the programme: the Emperor Louis Napoleon was a notorious philanderer who kept a string of mistresses at court, but "for the sake of decency" they had to be married, with compliant husbands who were bought off with government or court jobs for which they were utterly unqualified. Given that context, the exposure of the hypocrisy of the rich and powerful is razor-sharp and timeless. There are also some gloriously surreal moments: the dance which Périchole and Piquillo perform with their "jolly gaoler" is straight out of a Monty Python sketch.

Generally, I pity the lot of opera translators, who face a near-impossible task reconciling too many different aspects of the text. For this translation of La Périchole, Sams sidesteps the problem by making no attempt whatsoever at textual accuracy. He follows only the sequence and broad intent of who says what in the original, choosing instead to pack in as many gags, one-liners and clever rhymes as he can find space for. The result is a triumph, producing hilarity throughout without in any way departing from the spirit of the original. It may not be the most singable text - there was the odd line where the phrasing really couldn't be fitted into the music sensibly - but it worked like a charm.

The word "charm" applied particularly to the performance of Naomi O'Connell in the title role. O'Connell may not have the biggest voice you'll ever hear, but it's lovely to listen to (in tune, nicely lilted and unmarred by sharpness or excessive vibrato) and she has stage presence and magnetism to burn, helped by a gorgeously soft Irish accent. She also did a great job of the dance numbers - everything from the Spanish ones to a brief jig straight out of Riverdance. Robert Murray was an engaging Piquillo and made an entertaining couple with O'Connell, but I would have wished for something more from his solo set pieces, which give opportunities for a lyric tenor to shine that weren't really grabbed. A large ensemble cast performed generally well - the singing may not have been exceptional, but choreography, movement and acting were all out of the top drawer.

Francis O'Connor's sets were striking, making fine use of the fact that this is a long summer evening in a structure with transparent sides, so you get a lot of natural light. The Lima town square was bright, cheerful and spot on the original stage directions (although I'm not sure Offenbach would have foreseen the giant washing lines of multi-coloured underwear stretching over the audience), its transformation into The Viceroy's throne room handled magically, and the prison cell of Act III simple but effective. The show was stolen, by the way, by Walter van Dyk as the "Old Prisoner" who tunnels up from below the stage in act III and reappears (inexplicably with a bassoon) in the closing dance.

This production of La Périchole is the sum of many good parts: a title role performance with real star quality, feel-good music which excels in many different styles, inventive, attractive staging, and a superb translation of satire that retains its bite. Who knows: it could even give operetta a good name.