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I was trying to do RN analysis and encountered G7-Bᵒ7/C progression.

G7 can be considered as V7/VI so I assume Bᵒ7/C is C something chord to resolve G7.

Why does upper structure have to be Bᵒ7 (what it means in the progression)?

Do you think "C something chord" is as far as RN analysis should be done and simply be content with that "it just resolves G7"?

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I see it as G7 -> Cm7 so V-I in relative minor where Bo7/C functions more as a passing chord which is an altered prolongation of the dominant. So it is definitely not "resolving" chord, it builds up the tension before actually resolving on Cm7. Bo7 is a diminished substitute of G7 chord

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    @Sean Keep in mind that the chord symbols here are telling you what to do, not necessarily explaining the harmonic motion. Occam's razor says that the G goes to C, and indeed we get there just two beats later. The only difference between a G7 and a Bdim7 is one note, Ab vs G. We can view the Bdim7 symbol as describing passing motion; we don't have to go to heroic lengths to explain it as a chord in its own right. Commented May 15 at 13:42
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The easiest wat to conceptualize this is that G7 and Bo7 are basically the same thing. Bo7 is a G7b9 with no root and G7b9 would be an acceptable substitute for the G7 in this situation. The end result is basically a harmonic suspension where you arrive at the C root resolution on the downbeat but the G7 chord is held over from the previous bar and delayed till beat 3. I have done a lot of RN analysis but offhand I don’t know how to write this specifically. It’s basically a dominant chord with the tonic note in the bass.

Yes, you can listen to recordings and look at other lead sheets as other answers say but this one is perfectly acceptable for getting the basic feeling of this song. Lead sheets are guides, they are not etched in stone.

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Have you listened carefully to the original version? It's a 1930s recording. I just did, and I honestly could not say if that Bdim chord is really on a C or a B. (Bass is often rather muffled on these old recordings.) I would actually say it is on a B. The chord is then something of a sub on G7b9.

(I also checked a version of Peggy Lee which is later and clearer, and I have the same opinion. Another later one which is I think a rerecording of Benny's arrangment, it sounds like a G bass in some places, a C min in others.)

I would advise in general to treat these RealBook charts as no more than a guide. Always listen to at least one recorded version of the song. Very often you can find questionable harmonies or discover that various alternatives exist.

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...I was trying to do RN analysis...

On a lead sheet!

Be prepared to look at multiple lead sheets, and do the necessary transposing to compare them, then reinterpret the chord symbols for clearer harmonic function, before doing the RNA.

G7 Bo7/C Cm7

G7 can be considered as V7/VI

That makes sense to me.

I assume Bᵒ7/C is C something chord

I agree. The chord is not actually a Bo7, but the explanation is unfortunately a bit drawn out.

For the moment disregard the chord symbols except for the bass tones, that gives us a bass of...

G | C C

Now look at the melody...

F# G | F Eb

...that is F Eb over bass C, and contrapuntally that is a perfect fourth P4 resolving to a minor third m3. Technically, because of the exactly melodic motion that is an appoggiatura F resolving down to a chord tone Eb. But, because the F is a chord tone in the preceding G7, it also has a bit of a suspension feel.

I have to assume the person who wrote the lead sheet is treating the Bo7 chord, which contains the appoggiatura F, as a big appoggiatura chord.

In other words, the bona fide chords of the passage are simple G7 | Cm7, but by virtue of the actually notated melodic appoggiatura of F over bass C, the lead sheet author chose to expand that appoggiatura to four appoggiatura tones. Those four tones happen to make a Bo7 chord, so the "chord" symbol becomes Bo7/C. If it's voiced sensibly Bo7 should move smoothly to Cm7. You could probably move B > Bb, hold the D or move it to C, move F > Eb, and move Ab > G.

So, for the two measures, the RNA would be Eb: V7/vi | vi7 the appoggiatura and Bo7 "disappears in the RNA, because RNA does not deal with labelling non-chord tone motions.

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  • Seems to me it's a bit simpler. The chords in question tonicize Cm, which starts a ii V I in Bb which is the V of the key of the song. Commented May 16 at 3:53
  • @ToddWilcox, yes, but the little wrinkle is the suspension/appoggiatura part. That does make RNA of the first two beats labeled Bo7/C a bit tricky. Commented May 16 at 18:04

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