Scales and Modes - A Brief Lesson in Theory

The earliest forms of scales have roots that go back to the ancient Greeks, named after their most important tribes - the Dorian, Phrygian, Lydian, and Mixolydian. Each of them contained eight notes (from the root to the octave). These notes were the equivalent to the notes on the white keys of the piano keyboard, written in descending order.

The Dorian scale descended from E, the Phrygian from D, the Lydian from C, and the Mixolydian from B.

Musicians from the Christian Church adopted these scales in the Middle Ages. But for some reason, they decided to introduce various changes. First, they reversed the order, to make them ascending. Second, they changed the root notes. Third, they changed the term from "scale" to "mode." This made the formerly known Greek Dorian scale the Dorian Mode and made it from D to D, the Phrygian Mode went from E to E, Lydian Mode from F to F, and the Mixolydian Mode went from G to G. And the Greek Lydian scale, originally descending from C, now ascended from C and was renamed the Ionian Mode. Also, the Greek Mixolydian Scale, which descended from B, now ascended from B and was renamed the Locrian Mode. The scale that began on the A was called the Aeolian Mode.

This now meant that there were 7 modes - one for each of the white keys. We have already seen that the characteristic sound of any scale or series of notes is determined by its step-pattern of tone or semi-tone intervals. Since each mode has its own step-pattern, each mode has it's own sound.

In the Middle Ages, the modal system was the source of melody. By the 16th Century, the increasing complexities of "polyphony" (music which contains 2 or more harmonized melody lines) were leading to the breakdown of the modal system.

There was a new harmonic language being developed as the 17th Century began. The concept of "tonality" was expanded to include the key system (which is another lesson). All music had a "key signature" which identified the tonic (or first) note of the scale as the "key-center" or "home key." The intervals between notes were fixed by their distance from the tonic note or key center.

The heart of the key system was the concept of diatonic major and minor scales. A "diatonic" scale comprises the notes proper to the key. The diatonic major scale has the same pattern of tones and semi-tones as the medieval Ionian Mode (started on C), and the diatonic natural minor scale has the same pattern as the Aeolian Mode (which started on A). The resemblance, however, is one of structure, not usage.

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