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Recently I watched this video which discusses secondary dominants and specifically for the case of A II - V - I in the key of C.

They play a secondary dominant for the II chord, so they are playing an A7 chord.

I took some time to think of what scale I could use to improvise over it, here was my thought process:

We are playing in C major so our main notes would be:

C D E F G A B

When we are going to improvise on top of the A7 - we would like to include notes from the D Dorian scale, because this one only contains notes from C major still. (D E F G A B C)

Modifying that to match with the A7 we can raise the C to a C#, to get D E F G A B C#, which is D Melodic minor.

So would we could improvise with D Melodic Minor over the A7

After watching the video they decide to use a D Harmonic Minor which uses the tones:

D E F G A Bb C

I asked the creator of the video if we could use D Melodic Minor, and got this responce:

No, mainly because the sound of a dominant in minor is usually from Harmonic minor and in the context, Dm7 is a subdominant chord, and the note that signals that the progression moves to the subdominant is a Bb which is the b9 on A7.

Could someone explain why my reasoning is flawed and what it means for a note to signal a progression to move and why in this case the Bb would do that?

Thank you.

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Jens Larsen has some great videos, I think that in this case he didn't have time for a comprehensive answer to your question, and instead opted to justify why he made the choice in his video to play it as D Harmonic Minor rather than D melodic minor, given that in the video he is really trying to emphasise how he's trying to create lines that really emphasise the movement from chord to chord.

It's absolutely true that you could use D melodic minor. This fits the A7 chord nicely and then on the second measure you can shift to D dorian ready for the ii V I. D melodic minor's raised (or natural) 6th degree is a B. Compared to the chord we are 'outlining', A7, this is a 9th. So if you play D melodic minor over the A7 you will be 'brushing past' the 9th on your lines. This is absolutely fine and will sound nice and useable, no worries.

Jens' lesson however is about making your choice on any particular chord 'propel' you to the next chord. In this case, making the A7 an A7b9 gives a slightly more 'high tension' secondary dominant, which wants to move a little more to it's tonic. As the A7 or A7b9 is acting as the V (secondary dominant) to a MINOR chord (briefly, a minor tonic), not a major chord, the addition of the b9 is more in keeping with what we tend to do when playing V i to a minor resolution. The reason is a normal minor ii V i naturally has a b9 on the V chord (it's because it's a phyrigian chord with a raised 3rd to make it a dominant chord).

So Jens' logic is that if we are temporarily treating the Dminor as a tonic, before turning it dorian and carrying on with our ii V I in C, then it stands to reason we would use the V chord that we usually use as a basis for a V i in a minor key, ie a 7b9. I say basis because you can really extend and morph this chord much more as your confidence increases.

You can easily create this A7b9 sound by including a Bb, the A7's b9. By turning the B in your D melodic minor scale to a Bb you now turn it into D HARMONIC minor, and include the tension tone that tends to push a V towards a minor tonic, in short you create A7b9 > Dmin.

For creating a line that pushes more towards the next chord this addition may be welcome, however, the choice is yours, and you can achieve a slightly more floaty and slightly more gentle cadence from the A7 to the Dmin by playing D melodic minor instead. This means your A7 chord contains the 9th and this tends to sound smoother than the b9. The choice is up to you, though Jens is on the money in terms of what people tended to do in a 'classic jazz sound' sort of context!

ADDITION; I can see on re-reading my answer how mine and Jens' proposed approach differs from yours. You were trying to find a way for the A7 to fit as much as possible with a following Dorian chord, and our approach was trying to make maximum use of the tension available by temporarily treating the D as if it was a minor tonic. This sort of thing happens a lot, with the 'arrival chord', Dminor in this case, shifting to something else at the moment we arrive. In this case, We set up an A7b9 to propel heavily to a tonic Dminor chord, but when we get there the C# relaxes to C, the D dorians b7, the Bb 'resolves' (sort of) to the B, the D dorians 6. We've achieved more tension and more bounce from one chord to the next, and the voice leading to get to the ACTUAL arrival chord, a D dorian not D minor, is neat and satisfying. Chord to chord movements in jazz are often their own little microcosms of tension and release to better propel through the music, though you absolutely don't have to do this, it just gives a very satisfying, dynamic sound rather than a more smooth and static one.

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    Great, I understand the reasoning behind this now and why one might choose one over the other. Thanks! – cuppajoeman May 7 at 17:08
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This is the way I'd do it but it's based on a more classically oriented basis than most.

A secondary dominant tonicizes the note a fifth below that dominant. It's short-term (not quite a modulation as a modulation would need a lengthy confirmation later) but the "target" of the secondary dominant may be considered the tonic over a short span. If the target chord is major, one just uses the major scale on corresponding to that chord (with chromaticisms if desired, but the major scale is the basis.) It's a bit more interesting when tonicizing a minor chord.

A common procedure (but not a necessary procedure) is to use the raised 6th and 7th steps of the minor scale when playing a melody over dominant harmony. Then use the lower ("natural") form when playing over subdominant harmony. When using tonic harmony, the raised 6th and 7th steps are used with ascending passages and the lower steps in descending passages. However, while the above may be a plurality, the "harmonic minor" (using the lower 6th and raised 7th step) is popular in all cases, especially in instrumental music. (This form also makes for a nice arpeggiation of the dominant ninth chord.) Also, people sometimes use all the procedures in the same piece. It's a matter of taste. The only melodic procedure that is almost always used is using the lower 6th step as the upper neighbor of the fifth step.

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This may be a lot simpler with a visual...

enter image description here

When he play D harmonic minor over A7 it has an implied Dm tonic. The important thing is the implication. You don't need to play the Dm7 of the next bar to get the implied dominant/tonic relationship in the bar with A7. The implications comes from the C# to D. That part is circled in red.

When the bar with Dm7 is actually played a D dorian scale is used. While the previous bar implied the Dm as tonic, it's actually played Dm7 a subdominant to tonic C. That part is circled in blue.

The take away from this is you don't view a chord in isolation but in relation to its tonic. IMO that's the weakness of the "chord/scale" system, it basically teaches chord in isolation connected to one or more scales with no explanation about why one or another scale makes sense for a given tonal context.

The response you got about haromnic versus melodic minor, the tone B, and the role of Dm as a subdominant don't really make sense to me.

My understand of minor chord symbols is:

  • m7 is for ii chords, subdominant function
  • mΔ7 is a i chord with a major seventh, tonic function
  • m6 is a i chord with major sixth, tonic function

So when A7 and a D harmonic minor scale imply a tonic Dm it would seem to be...

A7 (DmΔ7)

...where the parenthesis mean implied but not actually played.

When the music continues and the Dm chord is actually played it is...

Dm7 G7 Cmaj7

...using Dm7 to show the chord is a ii subdominant.

So the whole thing is more like...

Cmaj7 | A7(DmΔ7) | Dm7 | G7 | Cmaj7

The comment about B/B♭ and subdominant is kind of unclear to me as stated, but this is what I see:

  • B♭ is a tone of the subdominant relative to Dm
  • B♭ is a tone moving to the subdominant in C major, basically B♭ resolves down to A, that A could be part of a Dm or F chord, either being subdominant in function
  • B natural is the leading tone in C major, functionally the basic harmony would be G to C chords, but we don't want that, because the music is moving to a subdominant Dm7

The actual wording...

...the note that signals that the progression moves to the subdominant is a Bb which is the b9 on A7

...is opaque to me when it goes on to mention A7. A clearer wording might be...

...the note that signals that the progression moves to the subdominant in C major is a B♭...

That's a general truism about moving from C major to its subdominant F major. The fact that it could be a Bb in C7 to F, or Bb in A7b9 to Dm is finer grained harmonic detail.

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