THE title of Sir James MacMillan’s oratorio Angels Unawares is taken from Hebrews 13.2. “Be not forgetful to entertain angels, for some have entertained angels unawares.” The 70-minute work, for choir, tenor, and soprano soloists, with strings, timpani, harp, and trumpets, sets a long poem by Robert Willis, former Dean of Canterbury Cathedral, in 12 short movements depicting encounters with angels, six from the Old Testament and six from the New. The score is dedicated to his memory.

Commissioned by the Genesis Foundation for choir of the evening, The Sixteen, directed by Harry Christophers, it was first heard publicly in March in the Sistine Chapel. Its British première was in the Cadogan Hall on 2 June.

MacMillan’s usual skilful orchestration brings out the dramatic possibilities of the words, and the Britten Sinfonietta were eloquent exponents. We pass from the Exile from Eden, via Jacob’s Ladder to Gabriel’s Message and The Temptation in the Wilderness. Certain numbers stand out: the slightly oriental, hymnlike flavour of Elizabeth Watts’s soprano solos in Abraham and the Three Visitors; Mary’s passage from darkness to hope in The Song of Mary of Magdala and the tenor Matthew McKinney’s disbelieving refrain, “How could I not have known?”, as Tobias tells of his encounter with angels whom he did not recognise, each iteration differently coloured.

The choir, clear of diction and reverent of tone throughout, ended with a Vision of John, whose opening unaccompanied hymn melted into a War In Heaven represented by strings scurrying in confusion up and down the scale, culminating in the Tree of Life, whose leaves bring peace to heal the nations of the earth.

Much of MacMillan’s work is inspired by his own Roman Catholic faith. “At the work’s core”, he says “is an encouragement to show kindness to strangers as a spiritual discipline, recognising that every encounter could carry a significance that is deeper than is apparent on the surface.” The deliberate programming at the beginning of his Nothing In Vain, to a text by John Henry Newman with the words: “I shall do good, be an angel of peace,” served as a reminder to us all that we are here to try and be angels as well.

THE previous evening, rather than follow the usual classical-music practice and perform under the full blaze of the lights, in the Barbican Hall, London, the nine singers and six instrumentalists of the French Le Poème Harmonique chose to present their programme of 17th-century Italian music from the Counter-Reformation with soft, shifting illumination, echoed in their soft gleaming sound and the music’s constantly shifting tempi. The stage looked like a painting by Caravaggio.

Two extracts from Marozzoli’s 1656 opera-oratorio La Vita Humana, a dialogue between Innocence, Pleasure, and Life, blurred the line between entertainment and spiritual edification. The martial strains of Monteverdi’s Pascha concelebranda were originally a warlike madrigal. Man’s victory became Christ’s in a lively Easter anthem with words by the 17th-century German Ambrosius Profe.

Luigi Rossi’s passionate lament of Christ’s crucifixion, Un allato messaggier, started life as Un ferito cavalier — a lament by the Queen of Sweden on her husband’s death. The delicious dissonances of Monteverdi’s erotic madrigal about the pains of unrequited love Si dolce è’l tormento proved equally affecting as Si dolce è‘l martire, a bittersweet meditation on martyrdom.

The evening’s major work was Gregorio Allegri’s 1639 Miserere. He didn’t actually write the version generally heard today: there is no definitive score. His setting of Psalm 51 alternates passages of plainchant with words set in falsobordone – a simple series of chords, leaving the singers to embellish the lines as they thought fit, as they would have in the Sistine Chapel, for which it was composed.

The group’s director, the theorbo player Vincent Dumestre, decides during rehearsal which sections should be ornamented, and suggests ornaments to the singers. The ones that work well are written down, and the singers ornament other passages spontaneously.

This version had a family resemblance to the one we know. The plainchant was delivered by a splendid tenor. Two groups, of four and five voices, alternated as the light played across them, and sprays of notes rippled above the harmony from different lines in turn. We were transported to another world. The return to reality as the main lights went on was slightly shocking.