Question from reader

One hears from time to time that the tritone used to be called "The Devil's Interval" and that "the Church banned it." Can you tell me, which church, when, and in what sense? Kind of hard to think of V-I progressions without the minor 7th in there, and the dissonance between the 3d and the 7th in that chord.

Dr. B: Corelli invented tonality, which means until some time around 1680 there was no such thing as a chord progression. A chord progression means you're progressing toward something. When you listen to Monteverdi c. 1640, he isn't progressing anywhere, but is doing modal based harmony. Tonality caught on very fast, and by Bach music is fully tonal.

This is the third time I have written that Corelli invented tonality, so perhaps I should explain this. It was accomplished through the use of chain suspensions. In Cecilia's concert La Scintilla played a Corelli piece, and it was full of these chain suspensions or suspensions in a series. A suspension requires a particular sequence of chords and creates a strong sense of resolution. With the use of chain suspensions the sense of resolution and movement toward the tonic becomes very powerful, even irresistable, and is present throughout the phrase.

Subsequent composers noticed that the drive toward the tonic was accomplished more through the selection of chords than the use of suspensions: thus the chord progression. Already by Bach each chord has another chord that it expects to resolve to.

It's modal harmony that forbid the tritone, and modal harmony is more characteristic of the Renaissance and earlier eras. In modal harmony there is a cadence formula to identify the mode and a certain amount of gravity around one other note, but that's all you get for harmonic organization. Movement follows the rules of counterpoint which doesn't really concern itself with what order the chords go in. The composer would stick in a Bb to fix the forbidden interval. By Monteverdi the number of modes in use corresponded roughly to the major and minor scales.

It was a silly rule, like the world is flat, intelligent design, that kind of thing.