'I' and 'O' : a Compositional Basis

Cyweirdant a Thyniad

 

The music was unlike other North European art music of the time, since it was not an unaccompanied melodic line; like plainsong, not a melody sounding against a drone; like much medieval bagpipe music, not a line of melody accompanied by an instrumental line or texture; like the troubadours' songs and not different lines of melody sounding together; like a polyphonic mass or a madrigal. 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). 'O's are usually made from the lleddfdannau, the movable strings or notes which do not correspond to the 12 : 9 : 8 : 6 set. The 'I's and 'O's are arranged into binary patterns, The Twenty Four Measures of String Music, Y Pedwar Mesur ar Hugain Cerdd Dant.

 

Page 107, Robert ap Huw MS, transcribed by Robert Evans

 

(107)

 

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] [ r. 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.

 

 

 

By permission of the British Library, Robert ap Huw, MUSICA, Additional 14905.

 

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.

 

By permission of the British Library, Robert ap Huw, MUSICA, Additional 14905.

 

 

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.

 

 

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.

 

  

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