How to fill the harmonic gap?

Question

So I have thought of almost the entire progression for my trio that goes from D minor to D major. Here is what I have of it so far:

D minor -> C major -> B minor -> ??? -> A major -> D major

And here is the harmonic relation:

i VII vi ??? V I

And here are the respective key signatures:

1b 2#

The C major can be thought of as D dorian, at least at the beginning of the section that has that harmony because of the C -> D motion. But this goes from simply being D dorian to being full blown C major. The C major -> B minor motion is where the key change occurs from 1 flat to 2 sharps.

Thing is, I have no idea what harmony to use to bridge the gap between B minor and A major. On the one hand, I could simply not have this bridging harmony and go from vi to V directly. But on the other hand, I am wanting this bridging harmony because I want to reserve the dominant chord for after D minor appears for a third time. Overall this is my harmonic plan:

Dm ---> Bm -> Dm ---> ??? -> Dm ---> A -> Dm ---> D

As you can see, I have D minor occuring 4 times. The short arrows are to represent the sudden appearance of D minor which in my piece represent cold snaps. The long arrows are to represent the chord progression going towards D major which gets longer each time before D minor suddenly appears again.

So without using the tonic major early on or going directly from vi to V, how can I bridge the harmonic gap between vi and V?

Answer 1

Because I wanted to make it sound as though it is approaching D major, I decided to use G major to bridge the harmonic gap. And I have finished my trio. It represents how in my area there are several bouts of spring weather before spring actually arrives. In the D minor section I use staccato notes in the piano to represent the snowfall, the fast notes of the violin to represent the wind, and the long notes in the cello to represent the person experiencing it. Every time D minor hits, it gets closer to the ultimate resolution. I use a lot of fugato early on to represent the uncertainty of whether it is an early spring or not.

The ending D major section includes birdcalls to represent that spring is here, and it even starts with a birdcall. The birdcall it starts with is a robin birdcall played by the violin. Then later on, there is a blue jay birdcall played by the piano. Then twice there are 3 birdcalls, a cardinal birdcall(it is the one with the quarter note followed by eighths), a robin birdcall, and a blue jay birdcall, first one at a time and then all at once.

Here is the link to my trio on Musescore:

https://musescore.com/user/50070/scores/5504586

Answer 2

Yes, I realise OP already finished the piece, but I'll explain this anyway for future curious readers.

I'm going to answer to explain why I think B♭ also makes a lot of sense:

Dm C Bm (?) A D

D minor: i VII ♮vi (?) V

I see a pattern here: The roots! D, then C, then B, then (?), then A. Play just those root notes, and one can immediately hear the pattern: It's a descending line. What note goes in between B and A? B♭. B♭ major, I think, would be a nice chord to continue that bass motion, especially if one is writing for blues, but even in classical styles, it could still be justified as an augmented 6th chord (include the 7th - aka augmented 6th -, then). To me, preserving that downward line is a cool effect, especially combined with the parallel modulation to D major.

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The author of this post, of course, eventually decided on a G chord, which is fine and sounds nice, and I've got no objection to that, but I'm just outlining another possible route to get to that V chord (and in this case, it has the added bonus walkdown root motion).