SHE has a mezzo voice as beguiling as any, a face to match and the ability to invest the most innocuous vocal phrase with depth and subtlety. Her sky-high reputation went stellar after Sophie’s Choice at Covent Garden, and there aren’t many about whom that can be said. So why did I come out of Angelika Kirchschlager’s concert of Bach arias with the Venice Baroque Orchestra feeling as one sometimes does after consuming a Chinese take-away: intermittently pleasured but substantially unsatisfied? One fault lay in the programming. Kirchschlager and this band have a Bach CD out; this is the tour of the album. But the notion of the mezzo delivering these testing arias without pause was clearly considered too tiring for her or us.

Instead, these great set-pieces from Bach’s sacred works — the likes of Bereite dich, Zion from the Christmas Oratorio and Schlummert ein from the (usually bass) cantata Ich habe genug — were interspersed with a succession of fizzy, Italian Baroque concertos. So having wrenched these arias out of context in the first place, Kirchschlager had to start afresh at rebuilding the contemplative mood each time she appeared.

If the interpretations had been judicious, all might have been well. But too often the arias lay too low for the Austrian’s lovely but light timbre, and Andrea Marcon, directing from the harpsichord, made little attempt to scale back the orchestra in sympathy. Phrase after phrase was masked. Kirchschlager should remind her conductor whom the public is really paying to hear.

Then there were the stylistic oddities. The Venetians threw their period instruments at the furious flurries of Vivaldi, Albinoni and Veracini with admirable energy, if not always immaculate intonation. Even the lutenist slapped his instrument like a bluegrass banjo. And two fine oboists floated through the languid Largo of the Concerto in D Minor, RV535, like a pair of gondolas gliding up the Grand Canal.

But in Bach the orchestra seemed soupy and sentimental. To make Erbarme dich from the St Matthew Passion sound like Mantovani is an achievement, but not one I would like to hear twice.

Oddly, when Kirchschlager ditched Bach and sang Vivaldi as an encore, she sounded at her most ravishingly uninhibited. She is set on a glittering path, but this Bach project was an ill-advised deviation. Angelika Kirchschlager Barbican

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