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Can anyone tell me what chord Bach notated in the second half of measure 91 in the score below? I can see that the first chord in this measure is FMaj7, which is the end of a circle of fifths chord progression from the previous measure (90)...and the chord in question is used as a function for modulating to a new key of A Minor (92 and 93 consist of E7 and A Minor, 94 is in the new key of A Minor). The Chord in question seems mainly based on D and B, with viola playing a whole note of A, some F's on flute, oboe and violin, and some C's on Trumpet, but I'm not sure which notes are chromatic and what is the main chord notated here. Brandenburg Concerto No. 2 Score

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  • Which line is the trumpet? Is it a C trumpet? – Dekkadeci Feb 5 at 5:35
  • can you tell me where you can see a FMaj7 in measure 91? (Note that the e in the trumpet is actually an a) – Albrecht Hügli Feb 5 at 8:37
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    @AlbrechtHügli Check out the E in the fifth staff (Violin I, I believe). – Richard Feb 5 at 23:20
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    @Dekkadeci the top line is an F trumpet. – phoog Feb 6 at 13:31
  • yes, Richard, I that's right: I7 – Albrecht Hügli Feb 6 at 13:43
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Since we're moving from a VI chord in A minor (first half of m. 91) to a V chord (first half of m. 92), standard practice suggests that the second half of m. 91 will be a chord that smoothly connects VI to V. Without even looking at a score, my guess is that the chord will be either a subdominant or supertonic of some type.

Looking at the score, the B in the bass strongly suggests a supertonic chord. Looking above it, we have B D F A, which pretty clearly lays out a Bø7 chord. With D in the bass, we're looking at Bø6/5.

The Cs in the trumpet are non-chord tones, either passing or neighbor depending on the circumstance. The same is true of the Es and Cs in the oboe.

Notice, then, that the circle-of-fifths progression that led into m. 91 continues, because F goes down a fifth to B, which goes down a fifth to E, which will ultimately go down a fifth to A.

  • Great answer, thanks Richard, sounds exactly right. I understand about the Bø7 chord, but would you mind explaining why the D in the bass makes it a Bø6/5? Thanks also for pointing out the circle-of-fifths continuation by the way. – John MC Feb 5 at 2:36
  • Also just a little confused after thinking again about your first paragraph...because the circle-of-fifths progression actually came from the key of D minor in m.85 (so it's D minor, G min7, C, F Maj7). So I'm confused about the F Maj7 being a IV chord in A minor as it seems the change of key has not been reached yet. Also wondering why a B would be used in this circle-of-fifths progression rather than a Bb (which key would the B be diatonic to)? – John MC Feb 5 at 2:56
  • @JohnMC The 6/5 is figured bass that indicates that it's a first-inversion seventh chord; I'm reading the D on beat 3 as the bass, but you could also view the B on beat 4 as the bass, putting the chord in root position. As for the Fmaj7, it's VI in A minor, not IV. We view this chord as being in A minor so that it's a diatonic common chord between D minor and A minor. If we wait until the next chord, the B isn't diatonic to D minor, so it can't be a common-chord modulation. The F chord moves to B, not B♭, since we're moving to A, which doesn't have a B♭! – Richard Feb 5 at 3:00
  • Excellent response, I'm super clear now, many thanks Richard! – John MC Feb 5 at 3:09
  • Sorry for misreading that about the VI chord by the way. – John MC Feb 5 at 3:17
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the modulation from F to am is introduced by Bm7-5 (am:IIm7b5)

(F:I => am: VI-ii-V-I46-V-I)

there is no F Maj7 in measure 91, and the f# on the last 8th note of measure 92 is the augmented 6th of the melodic monor scale.

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    Thanks Albrecht, and I see that f# now, thanks but do you mean the melodic minor scale? I thought the harmonic minor scale only raised the 7th? – John MC Feb 6 at 3:31
  • Yes, John, of course. I‘ll have to correct it. – Albrecht Hügli Feb 6 at 5:33
  • Thanks again Albrecht – John MC Mar 23 at 11:48

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