Have you ever wondered where the names for the notes come from? I mean the do, re, mi, fa, so, la, ti labels. They don’t even seem to mean anything! Well, I stumbled upon the answer in the last book I read, Stuart Isacoff’s, Temperament: How Music Became a Battleground for the Great Minds of Western Civilization.

Isacoff writes:

The impulse to explore greater musical horizons demanded advances in technology. In the eleventh century, Guido of Arezzo, a monk, of Pomposa, introduced an important one. He gave names to the notes of the musical scale — by taking the first syllables of each half-line of a hymn to John the Baptist — and created a musical staff on which to notate them. (The lines “Ut queant laxis resonare floris” yielded ut [today we use do] and re; “Mira gestorum famuli tuorum” gave us mi and fa; “Solve pollufi labli reatum” resulted in sol and la.) A new literacy illuminated the musical landscape. Portraying music visually made its structures easier to grasp and to vary; it enabled choirboys to learn in a few days what had taken weeks, and gave singers and composers newfound freedom to experiment. Musicians could more easily pose the question: What if …?

You’ll note that the last note, ti, is missing. Wikipedia explains:

The seventh note was not part of the medieval hexachord and does not occur in this melody, and it was originally called si from “Sancte Ioannes”. In the nineteenth century, Sarah Glover, an English music teacher, renamed si to ti so that every syllable might begin with a different letter. But this proposition had had no impact on the usage of si in the countries where si was already in use (in Romance languages, there is no confusion between the sound si and the sound sol).

This answers the question, but for one thing. I’ve never known the fifth note as sol. It’s always been so. I didn’t mishear it because the Do-Re-Mi song defines so as “a needle pulling thread” and not the latin translation of “sun.”

It turns out that the song as not nearly as old as I thought. Rather than a centuries-old tune, it’s barely older than I am. Oscar Hammerstein II and Richard Rodgers wrote the music and lyrics for their 1959 stage show, The Sound of Music. The Wikipedia entry for Do-Re-Mi notes,

So is an often-used alternate for the actual corresponding syllable in the solfège system, Sol.

And there, the trail ends. I’m still not sure why we often use so for sol, but that’s a small matter compared to all I’ve learned.

Oh, and the proper name for this note naming system is solfège. It comes from the Italian, via French, and is based on two of the notes, sol and fa. In fact, solfège is sometimes called the sol-fa system.