There are few more uplifting experiences than Bach’s Christmas Oratorio (Weihnachts-Oratorium), well performed, in a church, and at the right time of year. So to Chelsea’s St Luke’s Church, on the Saturday afternoon before Christmas, to hear the BBC Singers and the Academy of Ancient Music. It was very much a BBC occasion though, the outside broadcast equipment and personnel everywhere, and a spoken introduction by Radio 3’s Sarah Walker. Before addressing her radio listeners, she politely instructed we concertgoers not to cough, while understanding that this might be a difficult injunction to follow in midwinter. But the BBC had spoken, and coughs were there none. That could be due to the authority of the Corporation, or even to the robust health of the residents of the Borough of Kensington and Chelsea. But most likely it was because the sheer quality of this work kept everyone’s focus on the spiritual promise of the Christmas message.

Bach’s work consists of six cantatas or ‘parts’, which provide a sequential exposition of the Christmas story. This concert was of Parts 1–3, narrating the birth of Jesus, then the annunciation to the Shepherds, and finally the adoration of the shepherds. Much of the music was “parodied”, or recycled, from among his earlier work, including secular cantatas. So music that was arguably too good for its initial purpose of celebrating the birthdays of aristocrats, was given a new text and refashioned for the birthday of the Saviour. The full three-hour work was not designed to be performed at one occasion , but spread over the major feast days of the Christmas period. Here just the first three parts were given (without interval), with the second three parts to be performed next month.

It was very much a BBC occasion, with the Academy of Ancient Music almost as the pit band hired for the occasion. Thus no AAM programme book, just a BBC handout with the text and translation of the parts to be performed. The 24 BBC singers were all listed by name, but there was no indication of which of them was singing the various solo recitatives, arias and duets. Is there a sort of BBC Singers’ code or omertà on the matter? (After all they can reasonably claim “We are excellent professionals and any one of us could sing solo music for our voice type”.) Each soloist went into the pulpit to sing their solo item, then returned to the choir for the next choral item, close perhaps to what Bach expected. Singers given a solo in the first cantata yielded solo honours to another in the second, and yet another in the third part – strength in depth indeed. They were all good, some very good, and with a quite excellent Evangelist (the same tenor throughout). They even broke the code to allow him a solo bow, if not an actual name.

The splendid opening of the first part “Jauchzet, frohloket, auf, preiset die tage” (Rejoice, be glad, come, praise the days) could hardly be more upbeat, with its pealing trumpets and unusually active timpani part punctuating a wonderfully celebratory chorus. The BBC Singers sounded as ecstatically joyful as if they brought this music not from the rehearsal room but straight from the manger. The mezzo soloist was rich-toned and immaculate in period style, and the bass relished his superb aria with obbligato trumpet. The first chorale is well-known from its various occurrences in the St Matthew Passion, and perhaps Sofi Jeannin’s slow tempo reflected its sorrowful role in that work more than its context here. The lovely pastoral Sinfonia that opens the second part was pretty broad too – perhaps a choral conductor instinctively adopts a ’breathing’ tempo in slower music. Certainly the speed allowed the strings and Baroque oboes of the AAM to produce a beautifully evocative sonority. As did the obbligato flute of Rachel Brown in the tenor aria hastening the shepherds to go and “behold the lovely babe”.

Jeannin was at her best in the large choral numbers of each part, coping heroically with a tricky acoustic. St Luke’s boasts the highest nave of any London parish church, and at times the denser textures suffered – as one vocal line bounced back from the roof 60 feet above the singers, so it met with its successor on the way up. But Jeannin and her superb singers still elucidated the polyphony expertly. It might sound even better when broadcast on the 9th January, as the soaring lines were captured by BBC microphones a little closer to their point of origin.