The King's Consort, Wigmore Hall, London

In 1863, Rossini completed what was destined to remain his last substantial work, and added a little postscript. "Dear God, there you have it, finished, this poor little mass. Is it sacred music [musique sacrée] or is it damned music [sacrée musique] that I have created? I was born for opera buffa, as you well know! Little technique, a little heart, that is all. So may you be blessed and grant me Paradise."

Actually, at 75 minutes, the Petite Messe Solennelle is not so little; time enough to round up a whole motley range of styles sacred and profane. As if to emphasise its bemusing diversity, Robert King and his King's Consort chose to preface it in this New Year's Eve Wigmore Hall programme with the intense purity of William Byrd's Mass in Four Parts.

Published under plain covers in 1593, this was evidently intended for the private use of his fellow Roman Catholics, under duress in Protestant England, and the poignant suspensions of its final "Dona nobis pacem" have always been interpreted as a plea for release. Sung two voices to a part, at brisk tempos, in the utterly unecclesiastical acoustic of the Wigmore, this urgent, occasionally rough reading - so different from the usual cathedral-choir approach - seemed to convey all the more vividly how it must have sounded in the close, shut rooms of fearful, recusant households.

In the middle of the opening "Kyrie" of his Messe, Rossini, too, plonks down a fine paragraph of unaccompanied counterpoint to show he can do the old Renaissance church style with the best. But no sooner has the "Gloria" blasted off than we are pitched into a whole sequence of salon pieces and drawing room balladry - emphasized in this performance by the retention of Rossini's original scoring for two period pianos and wheezy harmonium, not to say the Italianate high camp with which the tenor, Charles Daniels, soared through the "Domine deus" section.

Yet the apparently straightforward litanies of the "Credo" cannot quite disguise a speculative, even experimental side to the music. Curious little modulatory schemes abound here, as though Rossini had set himself the task of seeing how many different keys he could glide through without anyone noticing, not least in the "Crucifixus", serenely floated by the soprano, Carolyn Sampson. There follows a solo piano prelude, like one of Liszt's starker late pieces; a dulcet "Sanctus" set in the style of a close harmony group; an "O salutaris hostia" in slow waltz time - and so it goes on to the end.

As performed with such style and relish, and so evidently enjoyed by a capacity audience, the Petite Messe almost seems to qualify as a postmodernist manifestation avant la lettre. Meanwhile, as metaphor, the pain behind the "timeless" polyphony of Byrd's mass remains as timely as ever.