Whether fortuitous or sly programming, all three operas performed by Chelsea Opera Group this season have featured nuns: Isabella, propositioned in Wagner's early comedy Das Liebesverbot; Leonora, about to take the veil in Verdi's Il trovatore when all hell breaks loose; and this evening, Rossini's Le Comte Ory. Here, it is the Count and his men who disguise themselves as nuns to sneak into the castle so he can have his wicked way with the Countess Adèle while her brother is safely away at the Crusades. A nun fetish? It's not an easy habit to break...

Presenting comedy in a concert performance is a risky business, particularly when that comedy relies on characters in disguise. I feared the worst in a staid Act I where Mark Milhofer's Ory – who is stalking the Countess Adèle outside her castle masquerading as a hermit – was in usual concert garb, albeit in velvet trousers and satin brocade jacket. To my relief, when Ory and his men turn up as nuns in Act II, seeking refuge from the libidinous count, they donned wimples over their evening dress and immediately the chuckles came. Props can be a dangerous thing though. A scorebound Adèle (Claire Booth) completely lost her place when trying to 'read' the letter from her brother and Milhofer had to cope with a a recalcitrant habit which kept slipping back. He eventually discarded it, only for Booth's Adèle to mischievously signal him to put it back on, at which point he threw it over his face like a veil, having to peek under it to take a look at his score. A high degree of camp perhaps, but betraying signs of under-rehearsal.

Whether comedy or opera seria, Rossini's vocal writing makes demands on singers that can cruelly expose a lack of technique. The singers here all managed creditably, although curiously only one of the seven – Margo Arsane's delightful Alice – had secure top notes. Milhofer has just the right metallic tenorial ring for Rossini and launched straight into his aria “Que les destins” fearlessly, but he has a tendency to cover the top note in a phrase, as if shielding it from harm. He was strong in ensembles and hammed up the role nicely though, and you sensed he was having the most fun.

Claire Booth has quite a flutter to her soprano but she attacked the role's coloratura boldly, even if slightly recklessly. It was certainly exciting singing, accompanied by a lively platform manner, one hand on hip, the other semaphoring her ornamentation. Booth did remarkably well not to corpse during an especially violent Rossinian storm, as the result of which the percussion section could be up on assault and battery charges, gong stand threatening to topple over. Heather Lowe was a sparky Isolier, the Count's page who also has designs on Adèle, overcoming a few early sour notes to sing with engaging freshness. The 'bedroom trio' with Ory and Adèle was a musical high point, even if a lot of the comedy got lost at this point.

Steven Page, peering over his spectacles as Ory's Tutor and singing in fruity French, was nicely irritable, adopting a safety first approach to the faster passages in his big scene. Benedict Nelson, singing Ory's pal Raimbaud, occasionally laboured in the bass role's upper reaches, but negotiated his way around the mountain of text well in his aria where his drunken 'nun' relates his military campaign to raid the castle cellars. Anne Mason's Dame Ragonde was sturdily sung, while Margo Arsane's bell-like clarity shone as brightly as her superb French diction.

Toby Purser, although let down by pedestrian string playing and thinness of tone from the COG chorus, attacked the score with plenty of braggadocio, Italian swagger and French farce combining to raise some much needed laughs this weekend.