In diminution the perfect longs are replaced by perfect breves, preceded by a perfect semibreve.
The pairs of crossed breve rests (pausas transfixis) retain their normal value - thus each pair is equal, in modern transcription, to a dotted semibreve rest.
The range of the tenor is only a fifth, discounting a solitary semibreve d in bar 83/41.
In his twelfth rondeau is found an example of a brevis divided into four semibreves.
Moreover, the occasional odd extra semibreve in all parts is accepted editorially into a bar so that cadences always fall at the beginning of a bar.
I was particularly pleased to see a serious discussion of the possibility of semibreve equivalence between signs, for there are musical sources where this provides the simplest explanation.
The difficulty was compounded in the later half of the 13th century, when the lozenge shape came also to be used for the semibreve.
A whole note (semibreve) divides into two half notes, a half note into two quarters, etc. and other notes are made by tying these together.
