The Bartholomew Consort's a capella recital in Summertown last weekend was a revelation - an exploration of little-known, late 15th-century choral works, sung with exceptional purity, eloquence and confidence. No half-hearted, tentative approach this; the choir was in full throttle throughout, driven to ever greater heights by their inspirational conductor, JanJoost van Elburg (pictured). Only in John Nesbett's setting of the Magnificat did the sopranos waver a little, the difficult top line occasionally sounding a little strained and uncertain. Otherwise, this was a bold and sparkling performance from a largely amateur group, whose members range from interior designers, IT consultants and fund managers to teachers, psychotherapists and professional musicians. Although an Oxford-based choir, the singers come from all over the British Isles and - incredibly - rehearse for a mere three days before each concert.

Sunday's offering focused on the recently-discovered and tantalisingly incomplete Eton Choirbook, a compilation of devotional songs drawn not only from Eton itself but also from the repertoire of the Chapel Royal and Magdalen College, Oxford, both of whose collections were later destroyed. So what we had here was a snapshot of the musical life of late-medieval English colleges, which also reflected the widespread preoccupation at the time with the Virgin Mary, as the Choirbook's contents are exclusively devoted to antiphons in her honour.

The incomplete state in which the book was discovered was brought sharply into focus in the printed programme, as details about many of the composers were incomplete. The two pieces attributed to William Cornysh, for example - were they written by one man, or were there two men bearing this name, who were father and son? Inconclusive evidence points, tentatively, to the latter.

The second half of the evening took us across to Europe, to hear similarly devotional music by Choirbook contemporaries. This included Obrecht's sublime Salve Regina, settings of Ave Maria and Gaudo Virgo by des Prez, and Gombert's Magnificat, which brought the concert to a suitably stirring finale.

The consort's next concert will be next February, and will comprise music inspired by the Song of Solomon. For more details, visit www.bartholomewconsosrt.co.uk