The Compositional Basis

This music (cerdd dant) was composed according to a binary system in which the eight notes or strings of the octave were divided into two sets: principal and weak, prinsipal a gwan. A typical division might be:

C, D, G (principal)
A,.Bb, Eb, F (weak)

corresponding closely to Boethius’ ‘fixed’ and ‘movable’ strings (De institutione musica, written before 510 A.D.) and the ‘hestotes‘ and ‘kinoumenoi’ of the ancient Greeks. The principal or fixed set is identified with the Pythagorean ratio – 12 : 9 : 8 : 6. Applied to the division of the monochord, this ratio gives rise to the octave, fifth, fourth and the wide, Pythagorean tone.

In cerdd dant a stave or line of music is divided into equal periods of time and each period is assigned either to the cyweirdannau (‘I’s) or tyniadau (‘O’s) the latter are usually made from the the lleddfdannau. A mesur or measure is one of the conventional binary patterns, The Twenty four Measures of String Music, Y Pedwar Mesur ar Hugain Cerdd Dant, the simplest of which is Tytyr Bach OOII OOII, the longest is Mak y Mwn Hir IIII OOOO IOIO IIII OOOO IOII. Sometimes the completion of a mesur once through is called a kaingk, in some cases shorter mesurau like Tytyr Bach should be repeated to make a kaingk.

Page 107, Robert ap Huw manuscript, transcribed by Robert Evans
llyma / r / pedwar mesur arhigain kerdd dant
Here are the twenty four measures of string music.
mak y mwn hir

IIII OOOO IOIO IIII OOOO IOII

korffiniwr

IIOOIOII . IIOOIOII

korsgoleff

IIOIIOOIOII

Rhiniart

IOOI.IOOII [sic] [recte.IOOII.IOOII]

koraldan

IIIOIOOIOOOI

tresi heli

IOOOIIIOOOIOII

wnsach

IIIIOOOI

kor dia tutlach

IOIIOOOIIOOIIII

korfinfaen

IOIIOII . IOIIOII

korwrgog

IOOIOIIOII

karsi

IOOOIOII . IOOOIOII

brath yn ysgol

IOIIOIOOIOIIOIOOIOII

fflamgwr gwran

IOII . IOIIOOIIOOII

mak y mwn byrr

IIOOIIII

kalchan

IIOOIIIIOI

bryt odidog

OOIO : OOIO : IIOI : IIOI

trwsgwl mawr

OOOOIIIIOOOOIOII

tytyr bach

OOIIOOII

mak y mynfaen

OO)IIOO : OOIIOOIIII

toddf

OIIOOOII

hatyr

OOIOII . OOIOII

mak y delgi

OIIIOII

alban hyfaidd

IOII . OIOO . OIOO . IOII

alfarch

OOOOOOOO IIIIIIII

Terfyn y pedwar mesur arhigain kerdd dant.
End of the twenty four measures of string music.

Page 107, Robert ap Huw MS, showing the names of the mesurau or measures and the mesurau in binary notation.

During a ‘I‘ the cyweirdannau are predominant and during an ‘O‘ or tyniad, the lleddfdannau are predominant. Generally the ‘I‘s and ‘O‘s are easy to discern in the bass part of the tablature. In the treble especially, notes or strings from the non-predominant set are recruited to make musical figuration. The bass is generally more stable than the treble. The figuration is not mere ornamentation. There are four main categories of figure each with one or more rhetorical functions.

Plethiadau, in English, ‘plaitings’ or ‘weavings’, these may begin a cyweirdant (‘I‘) or tyniad (‘O‘), may beautify between a ‘I‘ or an ‘O‘ and cause contention, each with the other.
Tagiadau, ‘chokings’, these are stops or rests between ‘I‘s and ‘O‘s.
Cysylltiadau, ‘joinings’ or ‘connections’, these join ‘I‘s and ‘O‘s.
Crychiadau, ‘wrinklings’ or ‘ripples’ (tremulando effects), these complete or perfect ‘I’s and ‘O‘s or come between ‘I‘s and ‘O‘s.

Detail of p. 35, Robert ap Huw MS, showing part of the key for reading the tablature. The names of the figures are written first, then the figures are represented as columns of letters with different signs above them, as they appear in the tablature. The fingering and damping for each figure is shown in triangular notation on a stave. Robert ap Huw has used the free space at the end of the line to write a fingering chart for the lower hand.

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