Cecilia Bartoli's latest project consists of an examination of the life and work of María Malibran, the famous mezzo-soprano of the early 19th century. As with so many of Bartoli's activities, both the enterprise and its presentation arouse mixed feelings. To replicate the work of a star, you have to be as good as that star - and we can't, of course, make the comparison, since Malibran lived long before the recording era. Bartoli's programme consisted of soundbites from some of Malibran's greatest roles - most notably Desdemona in Rossini's Otello - along with pieces expressly written for her. Many of the latter prove to be flashy show-stoppers: ironically, Malibran, the great tragedienne of the Romantic era, seems to have inspired music that in itself was vacuous.

As a technical feat, the concert was nothing if not heroic. Bartoli sang with apologies for a cold, though she refused to spare herself, completing a taxing programme and adding a generous selection of encores. On more than one occasion, however, you were aware that something was amiss. There was a tentativeness in some of her singing, an understandable unwillingness to let her voice flow.

Even so, Bartoli's gymnastic way with coloratura was very much in evidence in numbers such as Hummel's Air à la Tyrolienne and a chunk from La Figlia dell'Aria by Malibran's father, the singer-composer Manuel García. Elsewhere, however, she held back on a number of climactic phrases, so that the great cry of "l'ingrato" at the key moment in Desdemona's willow song seemed underpowered, and the final peroration of Mendelssohn's Infelice went for nothing.

Bartoli was accompanied by the Orchestra la Scintilla Zurich, directed by their leader, Ada Pesch. They are fabulous in Rossini, and we need to hear them more.