Johannes Ockeghem (c.1425-1497) was a Franco-Flemish singer-composer whose work was much celebrated during his long life (he may have been born closer to 1410). His setting of the Requiem Mass is the earliest of the polyphonic settings to survive. I recently reviewed an excellent performance of it by the male voice group Cappella Pratenis (Ockeghem, de la Rue: Requiem - Cappella Pratenis) and now another version arrives.

This one, however, is rather special. Paul Hillier, renowned choir-master and Director of the mixed-voice chorus Ars Nova Copenhagen, set a challenge for Danish composer Bent Sørensen to coalesce Ockeghem's 500-year old Requiem with some movements from the Requiem which Sørensen himself had already composed. Sørensen, retired from his professorship at the Royal Danish Academy of Music in 2011, always had an interest in looking back through musical history and combining the old with his brand of the New, so this was an attractive, but difficult project for him.

Ockeghem's Requiem only sets five movements of the Requiem's liturgy: Introitus, Kyrie, Graduale, Tractus, and Offertorium. The music is often austere, in two or three parts, but of great beauty and significance. Ockeghem was well aware of the emotional power and drama of the funeral Mass, where the relatives and friends of the deceased gather to say farewell, and deep emotions are carried by the music when the priest stops speaking. Sørensen too has an acute sense of dramaturgy in his compositions. He constructed a new Requiem Mass which embeds the unaltered Ockeghem and surrounds it with other movements which were prescribed by the Council of Trent (1545-63). some of these are his own compositions, others are plainchant, which brings in an even more ancient and fundamental form of religious music. The final effect is rather like the enclosure of a precious, ancient icon in a handsome, bejewelled golden frame.

It is very difficult to describe the music which Sørensen has produced here.He has great understanding of the human voice, its timbres and reactions with a surrounding acoustic. A rough comparison would be with Morten Lauridsen's choral music, intensely lyrical and constructed with shimmering tone-clusters and expressive dissonances. Remarkably, the new music dovetails with the ancient very smoothly, at times almost seamlessly, especially in the Sanctus, which is constructed of parts by Sørensen, Ockeghem and even some Monteverdi.

Ars Nova Copenhagen is acknowledged to be one of the most important European chamber choruses. The group particularly specialise in contemporary works, but they have a wide range of skills. This Requiem poses many technical difficulties, to which they rise with aplomb, producing a wide range of vocal colour and virtuosic singing with purity of tone and steady pitch. They are adept at creating Sørensen's intense mystical atmospheres with singing which is both plangent and numinous.

The Requiem was recorded in a venue with a large and marvellously responsive acoustic (its location sadly omitted from the booklet and digipak). In pursuing the drama of the piece, Sørensen wants the singers in several movements of the piece to be arranged around the listeners. Dacapo Records print two diagrams showing the disposition of the singers and microphone set-ups for the multichannel track. Engineers Preben Iwan and Mikkel Nymand used a minimal microphone capture. In the movements where the choir sing at the front in a semicircle, there is a Decca Tree array of 3 DPA4006-TL mikes (L,C,R), and at the rear of the auditorium a further forward facing Decca Tree with the same microphones (SL, SC and SR mixed to surround left and surround right). In the surround setup, with pairs of singers along the sides and a solo soprano behind the now rear-facing Tree, there are spot microphones (DPA4015-TL) at the side centre positions between the groups of singers..

Such positioning of the singers adds much to the unfolding drama of the Requiem, and the result is a perfect example of how to use the SACD's multichannel system. Sørensen's merging of the ancient and very modern musical styles produces a heady mixture of emotions, exciting not just the listener but the very reverberations of the auditorium. Hillier's long association and rapport with the singers produces singing of superlative quality, evidently satisfactory to the composer himself, who was present during the making of this recording.

A unique form of the Requiem Mass, of great interest to collectors of choral music, and a totally immersive sonic experience. Enthusiastically recommended.