I am trying to understand the first couple of bars from Hancock's Driftin. How should I interpret it ? If I look at it as a F major then what is the function of A7 there ?

Here is a link for the Dextor Gordon's solo in that song.

  • I would think that the A7 is acting as a secondary tonic and that the Bb7 is a secondary dominant of the secondary tonic. – Caters Nov 11 '18 at 1:22

The problem here is that the chord progression is actually played differently than it is shown in several lead sheets. The second chord is not A7 but F7/A (actually Eb7/G because the original is in Eb). So the second chord just moves to the IV7 chord Bb7 (being the secondary dominant V7/IV). The fourth chord is indeed an A7 chord, and in that case it's important to know that the following chord is a Dm7 chord, so the A7 is simply again a secondary dominant leading to IVm7,

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  • I was wondering about the 2nd chord. The lead sheet I found (in E flat) showed a bluesy G flat in the melody over G7, but I wasn't sure I was hearing that in the recording. I'm not at a piano to try either way. – Michael Curtis Nov 9 '18 at 16:05
  • @MichaelCurtis:There's an Eb in the melody at that point, which would be the b13 of G7, not totally impossible, but that's not what I hear. – Matt L. Nov 9 '18 at 16:08
  • @MattL. Where are you getting your info about the second chord? I spent some time listening to this tune at the piano, and I'm still not 100% sure what's going on. During the melody, Herbie plays a pretty clear G7 on the "and" of 3 every time, but this could maybe be interpreted as a chromatic lead-in to the Ab7. It's less clear to me what's happening during the solos, but Dexter Gordon plays a solid G7 lick at this place during his last A section, but otherwise the soloists don't really acknowledge it. Interestingly, Herbie uses the Eb blues scale exclusively for his second chorus... – Peter Nov 12 '18 at 15:06
  • @Peter: Interesting! I'm pretty sure that at least when the theme played the band is plays an Eb7/G chord and no G7 chord. I haven't analyzed what's going on during the solos, they might go crazy there. I can't give you a reference for that Eb7/G, that's what I hear (and I'm used to analyzing songs by ear). I do remember seeing this chord in that context transcribed somewhere else, but I can't remember where. – Matt L. Nov 12 '18 at 16:01

This progression moves to Dm, so the final A7 is definitely a V7/Dm, which is to say a V7/vi in the overall key of F.

As for the B♭7, this is a really common example where lead sheet notation doesn't tell the full story. Instead of viewing this as B♭7—that is to say, B♭ D F A♭—let's reinterpret that A♭ enharmonically as G♯. When we do this, we realize that this B♭7 is actually a German augmented-sixth chord in the key of Dm.

As such, we can understand most of this progression as an extended tonicization in Dm; your final two chords (B♭7 and A7) are actually Ger+6 – V7 in the key of Dm. And depending on our interpretation of the chord after F7 (some say it's A7, I think it's F7/A) we can even include that in the Dm tonicization.

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    I think your Bb7 interpretation is actually a bit far fetched in this particular case, because here it can be interpreted (and heard) as a IV7, an extremely common chord in a blues/jazz context. – Matt L. Nov 9 '18 at 17:14
  • @MattL. I agree that IV7 is common in jazz, but I prefer the augmented-sixth interpretation to make the move to Dm very clear. In essence, it's a modified ii–V–i into the relative minor, and I wanted to bring that out. (And augmented-sixth chords labeled as 7th chords are really common in lead sheets.) – Richard Nov 9 '18 at 17:28
  • @Richard Classically, this would be a great analysis, but I've generally heard that as being referred to as VI7 rather than the Ger+6. It's correct, but not common. – user45266 Nov 9 '18 at 17:29
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    Or rather, we hang out with different groups of nerds :) – user45266 Nov 9 '18 at 17:37
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    @Richard, perhaps the issue is that I7 to IV7 is extremely common in jazz even without any later movement to the vi. Anchoring the explanation of IV7 in the vi chord thus forgoes a very common function of the IV7 chord in jazz. (And we see this when we analyze the jazz genre more generally/broadly.) – jdjazz Nov 9 '18 at 22:16

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