The Rameau anniversary celebrations have tended, inevitably perhaps, to focus on his importance as an opera composer. He only began writing for the stage late in his career, however, and for their late-night Prom, William Christie and Les Arts Florissants turned their attention to an earlier period in his life and the three Grand Motets, his important contribution to sacred music.

The pieces are shrouded in mystery. They date from around 1715, though the third of them, In Convertendo Dominus, was revised in 1751. We don't know whether they were intended for church or concert performance. Their style – pictorial, vivid and emotionally immediate – pre-empts that of his operas, leading to discussion as to whether they are ultimately to be understood as devotional or dramatic.

As far as Christie is concerned, they partake of both qualities. He dissociates them from the operas by emphasising the comparative severity of their instrumental world, yet at the same time emphasises the close relationship between text, sound and atmosphere. So Deus Noster Refugium, which links divine anger with violence in nature, sharply contrasted with the pastoral of Quam Dilecta Tabernacula. The jolting emotions of In Convertendo Dominus were beautifully negotiated. Playing and choral singing had all the familiar Arts Florissants finesse, while the classy lineup of soloists included exquisite soprano Katherine Watson, mercurial baritone Marc Mauillon and the exceptional tenor Cyril Auvity.

Yet there were problems. The motets need a more intimate venue than the Albert Hall. Christie's insistence that the soloists should also sing with the choir was admirable, but having them walk from their positions behind the orchestra to the front of the platform for their arias and ensembles resulted in pauses between numbers, some of them so lengthy as to impede the momentum of the whole.

• The Proms continue until 13 September. Details: bbc.co.uk/proms.