Viderunt omnes... “All the ends of the earth have seen the salvation of our God” – this great Old Testament vision aptly sums up the inspiration for both the architecture of Notre-Dame in Paris and the liquid equivalent to be found in the Cathedral’s magnus liber organi – “the great book of organum”.

A picture postcard of Notre-Dame Cathedral tells you something of its form and appearance but little of its detail and none of its power: even the best efforts of imagination are not enough to appreciate fully its immensity until you are right there, standing next to what John Julius Norwich neatly summarised as the “first cathedral built on a truly monumental scale”. Likewise the music written for the cathedral needs to be heard as near to lifesize volume as feasible to understand its intensity and force.

Visitors to the Cathedral of Notre-Dame are first of all struck by the imposing Western façade, but on entering the building the experience is transformed by what Abbot Suger of St Denis, one of the forefathers of the Gothic style of architecture, had conceived as “the wonderful and uninterrupted light of most sacred windows pervading the interior beauty”; then there is the awareness of a vast mass of people contained within the towering walls and arches; and above all, the unmistakable sound of distant voices and movement reflected from innumerable ancient corners. For the Parisian musicians and worshippers living in the late twelfth and early thirteenth centuries, however, this was a dynamic experience as the new structure slowly took shape above the city skyline: a building project that would span several generations from the laying of the cornerstone in 1163.

Léonin, who was considered the master of polyphonic composition in his time and who appears to have been responsible for the magnus liber in its original form, must have spent much of his career in the unfinished ‘choir’ or Eastern end of the Cathedral, separated from the regular sounds of construction by some kind of temporary screen which perhaps was moved column by column westwards over the years. By the time Pérotin made a new edition of Léonin’s magnus liber and added his own massive polyphonic versions of two Gradual chants, most likely for feast-days in 1198 and 1199, practically the entire space of the Cathedral was ready to resonate in sympathy. Over the next halfcentury and beyond work continued on the building until it was as complete as it ever would be.

Certainly that is the story that seems to be corroborated by the enormous body of music in the magnus liber itself. The foundation of this repertoire is plainchant, unmeasured melodies associated with every liturgical moment in the Church’s calendar. Viderunt omnes 2 is a chant for Christmas Day and its octave, the Feast of Circumcision.

There are two very simple ways of constructing polyphony out of plainchant: either by adding a drone, one note held on as a pedal under the plainchant, or by simultaneously singing the same plainchant at a fixed interval above or below (the most obvious example is of men and women, or men and boys singing the same tune an octave apart). The ninth-century treatise Scolica [or Scholia] enchiriadis demonstrates this spontaneous and unwritten practice of parallel organum with a number of examples which we have recorded here as individual verses of a psalm 30.

On top of these early edifices in Western polyphony we can imagine ad hoc experiments in the performance of plainchant in a measured style (with each note either the same length or twice as long as the next), and in the improvisation of a free part over the existing plainchant. Today it is easy to forget how well these tunes, especially those for feast-days such as Christmas or Easter, would have been known by both the professionals in the choir and the congregation in the nave.

The two-part music or organum duplum from Notre-Dame most commonly associated with Léonin 3-16 is built upon all these earlier developments, with the familiar tune of the plainchant either slowed down while a second part elaborates a clearly soloistic line (organum purum), or rhythmicised into the same ‘modal’ system as the new solo line (discantus). The rules for unravelling thirteenth-century notation are relatively unambiguous for discantus or discant style, but they leave us with plenty of rhythmic options for the longer, more virtuosic sections of organum purum – on this recording we have explored a number of the many solutions (compare tracks 3 and 9).

It was the more regular discantus sections which proved most memorable and consequently attracted the attention of up-and-coming composers, including Pérotin. One section from the Viderunt omnes in particular, with the single, crucial word “Dominus” (6 and 12) became favourite fabric for rhythmic and harmonic experimentation, and many new two-part versions of this section were composed (including tracks 17-21), either to be inserted as substitute clausulae or possibly as free-standing pieces. In the furnishing of new words to the upper part in Factum est salutare / Dominus 22 there is the audible framework of the motet, which was to become a separate musical structure with a future far outside its original liturgical setting.

With the addition of a third, and then a fourth voice, the rhythmic organization of the discant style of organum was fully extended to the upper parts throughout, just as the Cathedral’s original arcade, gallery, triforium, and clerestory had to be carefully coordinated. And just as the exceptional height of the Gothic style of architecture required new solutions to the problems of this scale of weight-bearing, there were also further harmonic implications of combining so many voices – composers had to discover how to balance intricate mixtures of consonance and dissonance (harmonic intervals which sound relatively more or less pleasing to the ear) over a long span of time. According to an Englishman visiting Paris in the later thirteenth century (the posthumously-labelled ‘Anonymous 4’) it was “Master Pérotin who made the best quadrupla”, and it is these earliest surviving examples of four-part harmony which open the manuscript Florence, Biblioteca Medicea-Laurenziana, plut. 29.1 (‘F’) from which the editions for this recording were largely made. Our approach on this recording has been to combine what we know of twelfth- and thirteenth-century notational theory with the practical results of our own encounter with this celebrated style; above all, we have aimed to adopt a pace and an intensity to match the scale of the building for which this music was written. If, as for today’s visitors to Notre-Dame or for the scribe of the manuscript known as ‘F’, it is size that creates the best initial impression, then go straight to Pérotin’s Viderunt omnes 23-28 or Sederunt principes 31, written for the day after Christmas when St Stephen the first Christian martyr (and co-patron of the Cathedral) was remembered. If, however, time allows listening all the way through from Pérotin’s freely-composed melody Beata viscera 1 to a four-part conductus Vetus abit littera 32, then it may be hoped that we shall have conveyed something of the staggering cumulative effect of a Gothic cathedral-in-progress.

Antony Pitts