The passage quoted below from the German writer Aribo clearly indicates that, as far as he
is concerned, rhythmic nuancing of the morula is out of the question as a didactic concern
and that duple durations are decidedly in, as per Guido. This passage apparently
exemplifies the simple and double nature of the morula by the durations of silences (probably
for breath at the end of musical 'distinctions') rather than the durations of notes.
Aribo Scholasticus, De musica (up to 1078)
Latin: Scriptores ecclesiastici de musica sacra potissimum, ed. Martin Gerbert, Vol 2, p215
Another observation about Guido's 2:1 ratio for morulae is made in the contemporaneous
Commentarius anonymus using the example of the melody of two words in the verse Adiuva
nos, Deus salutaris noster of the gradual Propitius esto. The words 'Deus salutaris' have
one note per syllable. Here, the word morula is clearly used to denote the compound
durations of the notes for the word 'Deus' (two notes) and 'salutaris' (four notes). Thus the
concept of a morula is presented as being maintained over multiple notes and syllables.
Latin: Expositiones in Micrologum Guidonis Aretini, ed. Joseph Smits van Waesberghe,
Musicologica medii aevi Vol I (1957) p149
Morula dupliciter longior est vel brevior, si silentium inter duas voces duplum est
ad aliud silentium inter duas voces. Eodem modo morula dupliciter est brevior, si
taciturnitas inter duas voces simpla est ad aliam taciturnitatem inter duas voces.
A duration is twice as long or short if [the] silence between two notes is double in
relation to another silence between two notes. In the same way, a duration is twice
as short if [the] silence between two notes is simple in relation to a silence between
I affirm that the duration is doubly shorter
or doubly longer than itself, just as in the
gradual verse Adiuva nos, Deus salutaris:
'Deus', where there is a duration, has after
it a duration 'salutaris' doubly longer than
it, when it is itself doubly short, because it
does not itself have but two echoed notes
and 'salutaris' four, and this is double
Morulam dico duplo breviorem vel duplo
longiorem se, sicut in Versu Gradali
"Adiuva nos deus salutaris", "deus", cum
sit morula, duplo longiorem se morulam
"salutaris" habet post se, cum ipsa sit
duplo brevior, quia ipsa non habet nisi
duas voces repercussas, et "salutaris"
quattuor, et hoc est dupla proportio.