The 6/8 section of JS Bach’s Komm, Jesu, komm (bars 79-167)
The 6/8 section falls into four sub-sections, each 22 bars in length, beginning at the upbeats to bars 79, 101, 123 and 145.
Structure of sub-section 1 (bars 79-100)
SubBars
section
1
79-100
= 22 bars
Choir 1
Choir 2
Key
1 bar
2 bars (modulating)
8 bars
Repeats, reharmonised
Imitates, varied
Repeats exactly
E flat major
C minor
The first three sub-sections work the same or similar thematic material in three different, progressive keys, C minor, G minor and D minor.
But because the keys move up by an interval of a fifth each time, some parts (mainly Sop and Alto) are swapped around to keep them within
singable range. The bass line remains always the same, apart from transposition; therefore the Tenor line becomes most liable to alteration.
Content of the 8-bar repeated passages
SubBars
Key
section
1
85-92
C minor
93-100
2
107-114
G minor
+ 115-122
3
Content
Choir 1 introduces first version
Choir 2 repeats exactly (with only the upbeat chord different)
S = basically A at 85/93, but modified (about 50%)
A = S at 85/93 exactly
T appears to be completely new
B = B at 85/93 exactly
129-136
D minor S = S at 86/94 – 92/100 (except for a few notes in 132/140 borrowed from T in 88/96)
+ 137-144
A starts as S at 107/115, then at 131/139 reverts to A at 87/95 with slight modification at 1352/1432
T = S at 84/92 – 881/961 with modifications, then from 1322/1402 as T at 882/962
B = B at 85/93 exactly
In the fourth sub-section, after the initial antiphonal exchange (145-6), the texture broadens out to eight real parts (147-155). In this case, the
second half, instead of answering the first half antiphonally, it is an exact repetition involving both choirs, which serves as the climax of the
whole piece.