There has always been discussion concerning harmonic implications in contrapuntal writing. Voice leading in and of itself can be enough to generate interesting music, but without a clear harmonic plan the music will lack direction. Since J.S. Bach is the acknowledged master of counterpoint and harmony I will use what I thought would be a fairly simple piece to demonstrate the coexistence of these two musical principles: the Bourrée from Lute Suite 1 BWV 996. This is such a well known piece that I think everyone who reads this will know it in some capacity. My intention is to take a basic two part contrapuntal texture and indicate what I believe are the harmonies implied by the two tones. Or, if Bach were to compose this piece as a chorale for four voices, what harmony would he use when filling in the inner parts?
My analysis shows the implied harmony above the staff using chord symbols with Roman numeral analysis below. The harmonic rhythm is at the quarter-note level or on every beat as would be common in most Bach chorales. The level of harmonic complexity in this little piece is staggering. Bach actually uses all the notes of the chromatic scale within these twenty-four measures generating all kinds of interesting harmonic relationships!
There are several passages in which three voices are implied: measure nine (beats two and four), measure ten (beat two), measures thirteen and fourteen (beats two and four), measures twenty-one (beats one, two, three and four) and measure twenty-two (beats one and two) for example. These as well as other measures where skips occur in either the melody or bass line imply three part texture. This makes the job of harmonic analysis much easier. You may notice I did not include the D# in measure twenty-one, beat three in my harmonic analysis. I decided to hear it as a chromatic neighbor or chromatic passing tone to the following E and not as part of a G augmented triad, although you could easily make the case for that analysis. Every altered chord is originally a function of some sort of chromatic voice-leading which becomes acceptable to the ear as a struck dissonance over time.
I would like to discuss a few more points of interest. As is common in many binary Baroque dance forms we have the basic key relationships of minor to the relative major and back again to minor. In this case, E minor moving to G major (relative major) at the cadence of part one, continuing in G major in part two and returning to E minor by the final cadence. Part one consists mainly of ii-V-i progressions in E minor and G major.
Part two is where we really get the harmonic development. There are cadences in two new key areas (A minor in measure twelve and B minor in measure sixteen) as well as numerous secondary dominants within the passage beginning at the end of measure twelve through twenty. Bach uses a sequential bass line beginning on beat four of measure sixteen through beat one of measure twenty which generates the circle of fifths progression we know well in jazz: B7-E-E7-A-A7-D-D7-G-G7-C-F#m7b5-B7 and eventually Em to complete the cycle.
Of course many of the harmonies I indicated are conjecture on my part since we do not have full chords to work with. I do think my analysis is accurate and within what would be common practice during this musical period. Play the chord changes while singing the melody line or do your own chord/melody arrangement and I think you will agree the harmonies work quite well.
One other note: The circle with the diagonal slash indicates a half-diminished seventh chord or, as in jazz, a minor seven flat five chord. This type of chord is usually found functioning as the ii chord in a minor key as Bach uses it here and prepares or precedes the dominant (V).
In conclusion it is clear that Bach is always thinking harmonically. It is this perfect marriage of the linear (horizontal) and harmonic (vertical) aspects of the writing that makes his music so successful.