The Royal Academy of Music has a small but beautifully refurbished theatre, the 230 seat Sir Jack Lyons Theatre, where it stages full opera performances. Although many of the seats are taken by Academy staff, performers' friends and families, talent scouts and others with specific reasons for being there, some of the tickets are available to the public. I went along to see what they made of Così fan Tutte: the cast and orchestra are all RAM students, under the direction of the highly experienced John Cox and the baton of RAM's director of opera Jane Glover, who spent seven years as artistic director of the London Mozart Players and could therefore be said to have more than her fair share of form for conducting Mozart.

Così is a strange animal. On the surface, it's straight buffa farce, with the most preposterously silly plot: the idea is a truly batty one that our two faithful beauties will be taken in by the fake moustaches of their lovers and fall into their arms like ripe plums, and many of the plot twists and turns are arrant nonsense. It's all a vehicle for lots of fun, and to my ears, Lorenzo da Ponte's dialogue feels every bit as fresh, vivacious and light-hearted as it must have done two hundred years ago. But meanwhile, Mozart's music is screaming a different message at you: this love and romance thing is important and potent, ignore its power at your peril. I think it's the combination of trivial, light-hearted comedy and music that hits your soul directly which is responsible for Così's enduring popularity.

Student orchestra or no, I don't expect ever to hear the music played better than last night. The music had bite and energy throughout the evening - and it's quite long with nearly three hours of music. Jane Glover never allowed anything to drift, many subtleties of the score were brought out, the balance between orchestra and singers was spot on regardless of the volume level or the number of people singing, and there was some truly outstanding woodwind playing.

The production was set with appropriate humour in a university (the girls as music students, Don Alfonso as "Lecturer in Behavioural Science", complete with the words "Così fan tutte" transformed into a mock-equation on the blackboard. The set was simple but beautifully executed - graph paper wallpaper, models of DNA, mathematical solids and brains on sticks.

In acting terms, the performance was as good as anything I've seen from a professional company (and, I suspect, rather better rehearsed than most). Così has something of the buddy movie to it: for it to work, there has to be real chemistry between Ferrando and Guglielmo. Roberto Ortiz and Charles Rice played the scenes for laughs wonderfully and showed enough chemistry to blow up the lab, Mary Bevan played the cynical fast-talking Italian maid Despina to perfection, Katie Bray was a suitably flibbertigibbet Dorabella, and Ruth Jenkins ran the show as Fiordiligi: in spite of the daftness of her lines, she was totally credible in her angst-ridden transition from primness to infatuation.

You wouldn't expect the singing to be 100% perfect in a student production, however prestigious the institution, and it wasn't - but it came closer than one might have expected. All the six main singers were quite wonderful in the ensemble sections: trios, quartets and sextets were perfectly balanced and eloquent in their display of Mozart's elegance of vocal line and blending of voice types. The recitatives were a revelation: I had to pinch myself to remember that these weren't actual Italians conversing at speed with verve and gusto. Where the cracks showed a little was in the headline solo numbers: Ruth Jenkins has a very beautiful warm voice and a great deal of vocal control, but struggled towards the low end of her register, while Roberto Ortiz, who otherwise sang admirably, had some difficulties with his lament Un'aura amorosa. And it's inevitable that a very young voice, however good its quality, isn't going to sound right in a buffa bass part. Frederick Long sung Don Alfonso with great fun and musicality, but had no way to summon the world-weary gravelly voice that the role demands.

At the end of the evening, Mozart and da Ponte came out as the winners. The wittiness of da Ponte's dialogue and the aptness with which Mozart wraps music around them make Così fan tutte an immersive experience, and you leave the theatre with the message of the opera ringing firmly in your ears and heart: love is precious, hold on to it.

The Sir Jack Lyons Theatre is a lovely place to see opera - small, comfortable and with great acoustics. At the fraction of the cost of a professional performance, RAM's performances are one of London's better-kept secrets from operagoers. And if this is the quality of our future opera stars, it seems to me that we're in pretty good health.