Modulation: dominant, subdominant

Modulation is a shifting of key-center (the tonic), or "the key." A semitone alteration upward (whether by sharping or by removing a flat) at diatonic degree 4 makes the diatonic pattern reappear with a different tonic--a new key, the dominant of the old key. This changes the key of C major to G major, for example, or B-flat major to F major.

Altering degree 7 downward by a semitone (by removing a sharp or by flatting) re-forms the diatonic pattern with a different new tonic, the subdominant of the old key. This changes the key of A major to D major, for example, or B-flat major to E-flat major.

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A pattern-generalized explanation (without keyname examples) at the Squiggle article shows how the same diatonic pattern re-forms on first-degree modulation. The Circle of Fifths (Clock of Dominants) is a practical way of schematizing progress through the keys by first-degree modulation, in either direction: clockwise through successive dominant keys, counter-clockwise through subdominant keys.

"Slantnote" (David Zethmayr) 20:15, 2 December 2011 (MST)