Guido’s work was considered revolutionary and not in accord with the old ways which the church fathers reverenced. Because of plots against him, he was cast into prison. But the Pope, realizing his greatness and value, saved him. The inventors of new ideas always suffer!
Mensural Music or Timed Music
Before Guido invented it, there had been no system of counting time.
If you are studying music, you know all about time signatures and what metre a piece is in, from the ¾, ⁶⁄₈, ⁹⁄₈, ²⁄₄, ⁴⁄₄ or sign Ⅽ at the beginning of the composition, but you probably do not know how or when these signs came into use. In the Gregorian plain song and in Organum, there was practically no variety of rhythm and no need for showing time or marking off the music into measures. The accents fell quite naturally according to the words that were sung, much as you would recite poetry. But as music grew up and became more difficult, it was necessary for a chorus singing in three or four different parts, to sing in time as well as in tune, in order, at least, to start and finish together!
The first metre that was used was triple (three beats to the measure). It was called perfect and was indicated by a perfect circle,
, the symbol of the Holy Trinity and of perfection. Duple metre (two beats to the measure) was imperfect and was indicated by an incomplete circle,
. Our sign for common time (four beats to the measure),