So I am composing a piece for piano trio to represent the transition from winter to spring. I have finished the first part where it is all in minor, D minor to be more specific, to represent winter. It starts off with the piano representing snow with the staccato high notes and the violin and cello both representing the wind. Then the violin continues to represent the wind and the cello plays a somber melody to represent the person experiencing the wind and snow. Now, I want to have the music get a more major quality to it but I don't want to go directly to major. I want it to be gradual to represent the rise in temperature with a few bouts of minor to represent cold snaps.
How can I get this gradual move from minor to major in quality? Would I use modes like Dorian and Mixolydian, each of which is 1 step closer to the major scale? Would I simply introduce F# and C# while Bb is still being played or what? I want to keep the tonic of the piece as D while this minor to major transition is occurring.
Here is the progression that occurs in the winter theme:
Dm -> Gm -> Dm -> F -> Dm -> Gm -> Dm -> F -> Bb -> Gm -> Dm -> F -> Gm -> Dm
As you can see, it starts with the same 4 chords twice. Then the Bb chord is the place where it diverges from the original 4 chord progression.