About a thousand years ago the Church was facing a crisis. This is of course nothing new: the Church is always facing some sort of crisis. This one had to do with music.
For the first millenium of the Church's history composers had been creating music to go with every part of the Mass, along with the divine office, and general hymns of praise, and so on. The total of music was immense, and every last bit of it was in danger of being lost forever because no one could write it down. As St Isadore of Seville put it: "Unless sounds are remembered, they perish, for they cannot be written down." Early attempts at write music at that time consisted of arrow-like markings over the words, indicating if the pitch went up or down, and sometimes elaborate squiggles. However, such markings were mnemonic devices, aimed at helping someone who already knew the piece remember how it went. It would not have been possible for someone who had never before heard the song to pick up a piece so marked and sing it from the page.
Enter the hero of our story, Benedictine monk Guido d'Arezzo. Our hero was in charge of teaching music to the young monks in his monastery. While teaching them our hymn for Vespers on the Feast of St. John Baptist, he noticed that each line began on a successive ascending note:
Ut queant laxis
If you take the first syllables on which those ascending notes appeared you have Ut, re, mi, fa, sol, la, and si... If you were to change the "ut" to "do" (pronounced as in "a deer"- a female deer) and "si" to "ti" (as in the drink, goes well with jam and bread, so I'm told, I don't like jam) you have something familiar to us all. What Guido had done was give the notes names, and names can be written down. The issue was how.
Eventually the solution he arrived at was to draw four lines over the words, and mark one line either as "ut" or as "fa" and indicate the notes with square dots placed on the line or space over the word, thus indicating that word's pitch. And thus the first modern music notation was born.
He also created a method of teaching singers still used today, wherein singers are trained to sing the intervals by having the singers sing the notes out of order, rather like Julie Andrews in Sound of Music, where she teaches them, as Guido did, first the names of the notes, and them how to move between them "so, do, la, fa, mi, re, do- when you know the notes to sing." And his students could now sing most anything.
The immediate reaction to Guido's brilliant and workable solution was the reward so often given to those who find think outside of the box and find elegant solutions to complicated problems: He was fired by his bishop, who was upset that Guido turned novices into professional singers, instead of professional pray-ers. But another bishop of a nearby diocese was quite happy to have professional singers, and brought Guido to his place, where he encouraged Guido to write a book on his method. That book, the Micrologus, came to the attention of the pope, who summoned Guido to Rome to explain and demonstrate his new method. Guido did as told, and the pope, after seeing the method demonstrated, almost immediately ordered all monasteries to adopt Guido's methods and set down their music. And thus the crisis was ended.
But Guido's invention stretched far beyond the preservation of Chant. All the music that exists in the West today, whether Polyphony, or Baroque, or Classical, Romantic, Jazz and so on, exists because it could be written down by one writer, and handed over to musicians who could then faithfully reproduce what they saw on the page. And for that, we owe a tremendous debt of gratitude to a simple Benedictine monk, who was simply trying to teach his novices to sing.