Cerdd dant, literally the ‘craft of string music’, was a parallel craft or art to cerdd dafod, literally ‘the craft of the tongue’ or the craft of poetry. Both arts rested on profound and rigorous intellectual and philosophical foundations. Medieval Welsh poetry, like all medieval poetry, is the art of rhetoric brought under the rule of number. Medieval Welsh string- music, like all string-music, is the sound of strings regulated by numerical relationships.
The Pythagorean basis for musical theory was general in Europe and beyond in the late middle ages but Welsh high-art music of this period is unique in that it is not:
- a single melodic line; like plainsong,
- a single line for which an instrumental accompaniment has been found; like a troubadour song,
- the interweaving of many freely-moving lines; like a madrigal, or a melodic line moving against a drone; as in pibroch, the formal music of the Scottish pipes.
What the treatises describe and what we find in Robert ap Huw’s tablature is music made by separating, contrasting and carefully re-combining or mingling the notes of the scale, which have been divided into two sets, cyweirdannau and lleddfdannau, fixed and movable strings.
The two sets were part of Greek harmonic theory and were known as hestotes and kinoumenoi. The fixed set is identified with the Pythagorean ratio 12:9:8:6 and these ‘musical numbers’ are discussed by Boethius (c. 480-524), Cassiodorus (c. 490-583), Isidore of Seville (c. 560-636), and a host of learned medieval Christian writers who considered music one of the Seven Liberal Arts. The ratio 12:9:8:6, applied to the division of the monochord, produces the octave, fifth, fourth and tone, the foundations of ancient Greek and medieval European musical theory. The modern science of acoustics confirms the ancient observations. Musical numbers remained at the core of learned European musical thought into the 18th century. The fixed strings provide a stable framework for the movable strings, which by changing their pitch, yield the different scales and modes.
Ideas from the world of Pythagoras and Boethius are evident in Robert ap Huw’s MS as is the influence of Guido d’Arezzo (995-1050), whose sol-fa, stave and clefs we still use today. The cerdd dant treatises assume a thorough knowledge of Guido’s system and even though our only documents containing cerdd dant are in tablature not staff notation, that tablature is itself ultimately derived from Guido’s teachings. The cerdd dant treatises indicate that notes on the lines of the stave could be counted as ‘I’s and those in the spaces as ‘O’s. Evidently there are two ways of deciding whether a note should be a ‘I’ or an ‘O’, 12:9:8:6 or lines/spaces. Both ways are used in Robert ap Huw’s manuscript and in ‘Kaniad y Gwynn Bibydd’, pp. 36-7 of the manuscript, both ways can be seen working together.
Boethius discussed music as a single line of melody occasionally enriched by octaves, the harmony of successive sounds. Between the time of Boethius and the late-middle ages European musicians developed the art of simultaneous harmony and Robert ap Huw’s tablature is full of triadic chords. Even so, the music does not speak in the language of conventional late-medieval European harmony e.g. a triad in cerdd dant sometimes has an added sixth. A minor triad might have an extra tone next to the keynote. Cadences may end on a dissonance. The pieces written in Go gywair, the Sharp Tuning, have extremely dissonant passages. Two of the cyweiriau are pentatonic. There is no harmonic progression or signs of evolving functional harmony. Whole pieces of pentatonic music in a harmonic texture are rare in late-medieval European art-music. This is non-developmental music.