In the mid-14th century, an aging composer, blind in one eye and suffering from gout, embarked on a passionate relationship with a beautiful teenage noblewoman. He kept a record of their love in the form of songs, preserved in a book for her called Le Voir Dit. At least, that is Guillaume de Machaut’s version of events, and although it’s hard to tease out the truth from the elaborate coding and conventions of the courtly love tradition, and Machaut's own imagination, it makes a good story, especially when presented by the Orlando Consort, who dedicated the first part of their concert to a selection of Machaut’s songs, interspersed with commentary from the four singers to fill in the gaps.

Machaut’s songs offer considerable flexibility in performance: they can be accompanied by various numbers of instruments or voices and although the words can be fitted to the lower parts, the Orlando Consort’s approach was to add wordless vocal lines, allowing the single line of text to shine through clearly.

These songs deserve close attentive listening, for once you get your ear adjusted to the embellishments of Machaut’s meandering melodies and to the difficulties of medieval French pronunciation, the music reveals rich and expressive details and the four singers added colour by varying the combinations of voices according to the mood of the song. The three upper voices gave lightness and sparkle to Nes que on porroit les estoilles nombrer (Even if one could count the stars), and as the text moved to raindrops, sand and sea, Machaut introduces a gentle wave-like rocking rhythmn. The sobbing melody of the opening song, Ploures, dames, ploures vostre servant (Weep, ladies) immediately showed off the effortless grace of Matthew Venner’s alto. Le lay de bonne esperance was sung by tenor Angus Smith without any accompaniment, the solitary melody line spare and haunting. Sans cuer, dolens de vous departiray, a song of parting was given equal measure of sweetness and sadness by Mark Dobell’s honeyed tenor, accompanied only by sustained bass notes, delivered with absolutely unbending control by Donald Grieg. Although the prevailing mood was despair, Machaut chuckles to himself with a light, syncopated accompaniment as he encodes his beloved’s name in the riddling Dix et sept, cinq, trese, quatorse, et quinse.

Guillaume Dufay dominated the second half of the concert as the Orlando Consort made their case for numbering Dufay and Machaut “among the greatest in the history of Western music”. Dufay’s Missa Sancti Jacobi, probably composed in connection with the pilgrimages to the great shrine of St James at Compostela, is unusual in that Dufay sets the “propers” – those texts specific to the occasion – as well as the more familiar “ordinary” elements of the Mass (Kyrie, Gloria etc) and it was the Propers that we heard here. Dufay’s music is dazzling and bewildering in its rhythmic complexities and dense texture, but he gives his listeners moments of clarity in which we can regain our bearings: a beautifully fluid duet for alto and tenor in the Alleluia, bell-like tolling on the word “sonus” in the Offertorium and some startling, exquisite harmonies on the cadences.

The programme was rounded out with a polytextual motet by another medieval composer Jean Tapissier Eya dulcis/Vale placens, to remind us that however much the two Guillaumes dominate modern perceptions of medieval music, there were plenty of other fine composers too. The Orlando Consort are deeply attuned to the possibilities that this very old sound world offers to the modern composer, and included two works they have commissioned from Tarik O’Regan and Gabriel Jackson. The intervening centuries melted away as we heard these contemporary explorations of the music of the Guillaumes. O’Regan’s Douce dame jolie was based on another of Guillaume du Machaut’s songs. In the lively outer sections, Matthew Venner stretched a winding, passionate melody above a sunny, syncopated accompaniment in close harmonies, that at times sounded Caribbean; this contrasted with a plangent central section. Gabriel Jackson’s On the Bridge Over the Narrow River poignantly juxtaposes a poem on a wartime Good Samaritan theme by Richard George Elliot with prayers for protection, although the echoing acoustic meant it was very hard to follow what was happening.

Clarity returned after the difficult and troubling Jackson piece with two more works by Dufay. A simple setting of the Ave Regina was soothing and consoling. The final work Lamentatio Sanctae Matris Ecclesiae Constantinopolitanae lamenting the loss of Constantinople, was utterly grief stricken and here, Angus Smith shone through the other voices with his plangent tenor text, a short Old Testament verse in Latin, against Dufay’s own prayer in French sung by the other parts. These two showed a more intimate side to Dufay than the grandeur of the Mass, and gave a very moving end to an exquisite concert.