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This is Herre förbarma dig (Lord have mercy) from a Catholic prayer book. The chords are D-D-D-G-Bm7-C-D7-G. V-V-V-I-iii7--IV--V7-I. iii7-IV feels a bit odd. We have contrary motion between outer voice which is good. Even parallel motion between the bass & tenor and between the alto & soprano. I don't even see how the Bm7 fits in the key of G, and usually a 7th chord is a major chord with an added 7th - not a minor chord with a 7th. What is going on?

  • Yes but I mean that I dont see why the iii would be a 7th chord unless we wanted to move into a new key. Then we would use III7. – Hank May 29 at 15:31
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    @Hank, is it your understanding that 7th chords are only used when we want to move to new keys? – jdjazz May 29 at 15:51
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    Bm7 is diatonic to the key of G. – b3ko May 29 at 16:08
  • Actually re-reading this question I see a few misconceptions. I recommend googling “diatonic 7th chords” and “how to spell 7th chords”. Dominant 7ths are a major triad with a minor 7. Minor 7th chords have a minor triad and a minor 7. Major 7th chords are major triad with major 7. – b3ko May 29 at 17:58
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I would call the Bm7 a passing chord in this context. It's purpose is to smooth out the transition from I to IV. The pitches in this chord are all in the form of passing tones that link chord tones.

The composer further indicates the passing nature of these chords by putting them on a weaker beat (all of the other chords occur squarely on the beat, while the Bm7 occurs on an upbeat).

So all together, this iiim7 chord is totally acceptable. It does not really serve a harmonic function, its purpose is to smooth out the voice leading from I to IV.

Lastly, minor chords can have sevenths (so can augmented, diminished, and suspended chords). The purpose of a seventh is too add some extra tension, so it is great for key changes, but it can be used in many other contexts as well. Minor seventh chords are extremely common in jazz.

  • Great point about 7ths adding tension! @Hank, Peter's answer here further implies that the presence of a 7th often does not change the harmonic function. Further to Peter's point, the iiim7 chord not only occurs on an un-emphasized beat, but it also occurs only for a very brief duration. – jdjazz May 29 at 15:57
  • So in this case chord analysis isn't really all that perfect of an explanation. There is so much more than just chord analysis and roman analysis that we should do in this case? If so what is the name of the analysis used in the answer to my question? – Hank May 30 at 10:02
  • Identifying the chords is only the first step in harmonic analysis. The next set is the actual analysis of what the chords and their functions. You've correctly identified the chord as a iiim7, and now we are determining how it functions. In this case, it is acting as a passing chord instead of functionally, but that doesn't mean we've used the wrong tool. We've determined that this chord adds extra color and tension and smooths out the transition from I to IV, but it doesn't have much of an effect on the harmonic structure of this passage. – Peter May 30 at 16:14

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