Harmonic sequence is defined as a series of chords with a repeating
pattern of root movement. Following are some general
characteristics to look for in sequences:
A minimum length for a harmonic sequence is four chords–the
given intervallic relationship and one repetition.
The intervals of root movement refer to their letter-name
sizes. Down a fifth from F could mean either B or Bb,
according to the key.
Root movements not common otherwise are used freely, such as
ii-vi and viio–IV.
Any diminished triad may be used with its root in the bass (in a
In a minor key, use of the minor dominant (v) and the major
subtonic (VII) is common.
The sequence need not begin or end on the tonic, though it
Inversions may be used as long as the bass line itself displays a
melodic sequence. For example, a sequence may alternate
between first inversion and root position, resulting in the bass
line moving up a second and down a third.
The harmonic sequence is usually accompanied by melodic and
rhythmic sequence in the upper voices.
(The sequences described below are the most common, but others do
exist and are based on the same principles.)