Aroldo Royal Opera House, Covent Garden

What's the difference between a 19th-century German priest and a 13th-century Saxon Crusader? In a concert performance of an opera, not very much. When in 1856 Verdi reworked Stiffelio as Aroldo, it was in order to nullify daft amendments imposed on the earlier work by the censors: a married priest, whose wife has moreover committed adultery, simply wasn't on. When Stiffelio stiffed, so to speak, immediate changes ensued, including a distinctly uncatchy new title, Guglielmo Wellingrode.

But Verdi retained an affection for the opera and, six years later, got Piave to write a new libretto on essentially the same theme, although whether Aroldo improves on the amended Stiffelio is open to debate. The new version, vaguely echoing Donizetti and Rossini, sets the opera in Kent and on the banks of Loch Lomond (Kenth and Lago Loomond in Piave's pidgin). Aroldo's wife Mina has committed adultery (rape, the libretto implies) while he was away crusading and butchering the heathen foe. Most of the music of Stiffelio remains, but the final act, in which a confused denouement unravels at bewildering speed, is brand-new.

None of the narrative changes matter in a concert performance such as that mounted by the Royal Opera on Wednesday as part of its Verdi Festival. Few stagings would now observe Piave's instructions as to location and era, and in concert it's usually of little significance where or when the action takes place. In such respects, concert performances are inevitably compromised, but this was a spirited reading conducted with tremendous vigour by Carlo Rizzi.

The Stiffelio overture survives pretty well intact, screaming "Lights! Camera! Action!" as it hurtles forward. Alas, there was little action as few of the soloists seemed inclined to any gesture that might imply involvement. Nor were two mere concert performances deemed sufficient to warrant a set of surtitles, which meant following the libretto in the programme if one had any interest in the plot.

Aroldo was sung by Dennis O'Neill, whose mastery of the idiom remains intact even while the voice shows signs of fraying. Aspirates crept in, the tone was a little tough, but the phrasing was as lovely as ever. He was overshadowed, in both stature and vocal lustre, by Kallen Esperian, making her Covent Garden debut as Mina. She shapes her lines beautifully and her creamy voice hints at immanent melancholy: as she sings "Save me, almighty God", you just know it's a hopeless plea. Where O'Neill remained aloof from the drama, Esperian wrung her hands, clutched her breast and did all she could to suggest that this was a real drama. It was very impressive indeed.

Her father was sung by another Royal Opera debutant, Christopher Robertson, a dignified baritone with a tendency to blare at top volume but with plenty of intensity. Opera yields few opportunities to sing the role of Brian (here, Briano), and Miguel Angel Zapater seized his eagerly, thundering mightily as he reminded Aroldo of the right way to behave. The chorus was in fine form, notably in the unaccompanied "Angiol del Dio", immediately followed by an orchestral storm as menacing as the one in Rigoletto. Here, as throughout, the orchestra was at its fiery best. Carlo Rizzi knows how to floor the pedal without forcing the pace, and if Aroldo didn't quite emerge as a neglected masterpiece, it was no fault of his.

n Further performance: tomorrow, 7.30pm. Booking: 0171-304 4000