Choosing chords and a bass line

Each melody note can be the root, 3rd or 5th of a triad, or the 7th of a seventh chord. For each note, list the options, then choose chord and bass together.

In C major, a melody E could be harmonised with I (E is the 3rd), vi (the 5th) or iii (the root).

Choosing the bass

• Move in contrary motion to the soprano where you can.
• Move mostly by step. First inversions make this much easier.
• A good bass line is a melody in its own right: examiners notice a blocky one.

Strong root progressions

From strongest to weakest:

Root falling a 5th: vi to ii to V to I.

Root rising a step: IV to V.

Root falling a 3rd: I to vi.

Progressions to avoid

• Retrogressions: V to IV, ii to I, V to ii.
• The same chord from a weak beat to a strong beat, even across a barline and even with a new inversion.
• Three beats of the same chord: the harmony stands still.
• Only I, IV and V all the way through. It is correct but dull. Use ii, ii7, vi, first inversions and secondary dominants.

Restricted chords

iii: only under a descending 8, 7, 6 in the melody, or in a sequence. Anywhere else it sounds weak.

vii° in root position: avoid it. vii°6 works as a passing chord, but V6/5 or V4/3 is usually better.

6/4 chords are allowed in only three ways. Any other 6/4 is an error.

Cadential: Ic to V, with Ic on the strong beat.

Passing: the bass moves by step on a weak beat, for example I, V6/4, I6.

Auxiliary: I, IV6/4, I over a held bass.