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The Elements of Harmony > Single-note (in-depth)

Interrelationship between Melody and Harmony

Consider the first 4 bars of Bach's Chorale BMV40 (movement 6). Listen.

By considering all chords in the context of a Key, and reducing each chord to its basic chord
function, we are able to extrapolate the basic harmonic progression that Bach probably had
in mind when composing this chorale. This progression is shown in the line labeled "Harmonic
functions". The Figured Bass then follows from the basic harmonic progression in order to
produce a bass line free of contrapuntal errors with the melody (consecutive or hidden
fifths and octaves).

As an exercise, let's try to find another harmonic progression while maintaining the exact same
melody Bach composed.

One possible progression is Dm: i - i - iv - V7 - i Am: iv - i - i - VI F: VI7 - ii - V - I

This was obtained by selecting, at each beat, a Harmonic Function, and therefore a chord, that
contains the melody note. Consequently, at least one modulation away from Dm is obligatory in
order to accommodate the melody note "C" in bar 3. Furthermore, in order to avoid consecutive
or hidden fifths and octaves, inversions must be used. The final harmonization, including inversions,
is synthesized by the Figured Bass. Passing tones have been omitted. Listen.

Conversely, we can maintain Bach's original Harmonic Functions, and create a different melody. This
time, we must pick melody notes that are contained in the predetermined chords. Listen.

Note that, to avoid consecutive or hidden fifths and octaves:

on bar 1, beat 3, we have to double the 3rd, which is the least desirable choice for note doubling.
on bar 2, beat 1, we have to use a 2nd inversion, which greatly weakens the chord function.
on bar 2, beat 2, an F melody note would be impossible to harmonize without errors.
on bar 4, beat 1, the original ii7 chord function had to be changed to ii in order to proceed.

So clearly the two variables - Melody and Figured Bass - both influence each other. Some harmonic progressions may not be possible without changing some melody notes, and some melodies may not be possible without altering the harmonic progression. For this reason, it is advisable to develop these two aesthetics at the same time, to avoid cases where the appeal of one is unavoidably diminished by the blandness of the other. Listen once again to the full Bach chorale: it is evident how both melody and harmony are in far greater balance than either of the successive two exercises. In the first exercise, the harmony is much blander, and in the second exercise, the pleasing melody cannot, however, be fully accommodated by Bach's interesting harmonic progression.