A superb example of invertible counterpoint at the octave appears in Bach's monumental Fantasie [and Fugue] in G minor, BWV 542. Taking the two analogous passages quoted above, we see that in the first instance, in D minor, the soprano is a minor 6th above the alto. In the later statement, in G minor, these two voices start a major 3rd apart and are thus an inversion of the previous statement. The tenor is a literal transposition of the first statement, as is the pedal line.
Invertible counterpoint appears throughout the literature, especially during the Baroque era. But something quite fascinating takes place in this Fantasie regarding the voice leading at the cadences of the two excerpts. An additional voice appears [black square] toward the end of the 2nd measure in both cases. The tenor actually divides and becomes two independent voices [tenor 1 and tenor 2]. Now to the fascinating part: in the D minor statement, tenor 1 [B natural - up a major 6th from D below] crosses above the alto [G sharp - down a diminished 7th from F above] on the 4th beat. Both voices then proceed to A [unison] on the next downbeat. Needless to say, this voice crossing will have a bearing on how the organist plays the passage.
There is compelling evidence to support this assertion. Hint: it is directly connected to the process of inversion.
Comments are most welcome.
No comments:
Post a Comment