This was a representative sample of Mozart's sacred music: for Vespers, the evening service in the Christian churches, a brief Mass, a stand-alone Eucharistic meditation, a form of music supposedly inaugurated by Pope Innocent VI in the 1300s, and then an operatic aria masquerading as a religious motet, written for a Milanese castrato. Merton Music Director Benjamin Nicholas told me at the interval that Music at Oxford had wanted Mozart, and he'd obliged with a programme centred on the Vesperae Solennes from 1779-80.

Choir and orchestra immediately launched into the bouncing rhythms of the Kyrie, and then pressed on to the Gloria in rondo form, the music optimistic in accordance with the words. In the Credo brief solo parts were assigned to members of the choir whose contributions were a little variable in quality, notably in the soprano parts where notes at the bottom of the range often for amateur singers prove tricky; and so proved here. Moving on to the Ave Verum, Mr Nicholas conjured up from his choir a brooding sense of tension increasing as the piece developed over its short running time.

Then the orchestra led us smoothly into the Exsultate, jubilate with lyric soprano Milly Forrest as soloist. I felt for her as she appeared in a formal evening dress, given that Merton Chapel, far from full, was draughty, the audience huddled in coats. Although the concluding Allelujah is, of this most famous of motets, the most celebrated element with its extended coloratura passages – handled with supple ease by her - its true emotional core is the Tu virginum corona where her voice swooped high and low over the unde suspirat cor. Ms Forrest's pleasure in the music was palpable; all around me people were listening, looking and smiling broadly. The first-class programme notes (by Michael Nicholas & Jeremy Summerly) reminded us that Mozart was 16 when he composed the work. For a teenager to compress such a cornucopia of roistering exuberance and glorious melody into a simple cantata - I would have declared the thing an impossibility. And yet the fact remains...

The Vesperae Solennes (Vespers being the seventh of the eight offices of the monastic day) was composed for Salzburg Cathedral. It's heard as a whole relatively infrequently, though its Laudate dominum is a popular stand-alone aria for solo soprano. When in preparation earlier in the week I dug out the appropriate CD from my box of The Collected Works of W.A. Mozart, was that a sprinkling of dust on the cover? Shameful!

The setting includes five psalms and a Magnificat, with early on some bustling string writing, and then the austere Laudate pueri. In both of my two recordings of the aria, one from the Chamber Choir of Europe, the conductors keep up a funereal pace whereas Mr Nicholas led off Milly Forrest at a much more satisfying, brisker tempo, and she gave the pleading et in saecula saeculorum both drama and a sense of longing. I can't wait to hear her again.