Oboe Sonata in D major, "Fable" - I. In the Frog Marsh

Hey, guys! I just finished work on the first movement of a new sonata, this time for oboe and piano; it was a quick two days. I was first planning a piano sonata, but I shifted my mind over to a duet like this instead, a form in which I enjoy writing the most.

The sonata, I plan, will have three movements, and this is only the first. It has several main key areas/significant harmonies, and all of them are in mm. 30- 31. This is a piece with a story-without-words, with many motifs depicting the motions and movements of the eponymous frogs and of flowing and dripping water.

While much of the music could have been conceived of in 6/8, the music finally transforms starting in the frog dance at m. 156, wherein first the meter changes into the easiest conceptualization of the original music, then it shifts from duple into triple (i.e. the oboe's introductory line), and finally back into compound duple as its final transformation, all the while taming the bombastic eccentricity of the previous material, as well as the shifting harmonic language and chromaticism. 

Let me know what you think!

P.S. The type-facing is elementary and it will be adjusted in the final drafting process, when the following movements are done.

Interesting.

I wonder why, except for the few last bars,

you don't define the rhythm as 6/8 all the way through.

I also wonder, if you're going to perform it...

Oboe is known as a loud instrument and a piano can be a background instrument for it with it's top opened,

but the people who sit in the front might suffer from a serious headache, mainly if they came for a quiet classical concert.

So, did you consider putting the two instruments around ten meters away from the stage's front?

@Rabbival507 Thanks for the input! I could see the case for 6/8 in hindsight, definitely; I think part of the rationale relates to a fair bit of the melodic material. Even with the first bars of the piano part, I was composing while thinking of the melody (and in those bars, the harmony as well) in 2/4. I might definitely consider returning to the piece in the final drafting process (wherein I rewrite and recompose the entire piece) and putting it in 6/8 in most instances. I quite enjoy the idea of the narrative, even if it is trivial (and unnoticeable to the audience).

Also, you make an interesting point on the balance of the sound! My hope is that this could be easily worked out in practice, and that isn't necessarily a main concern to me at the moment (the thought certainly crossed my mind that it could be rather loud). Thanks for the suggestions, and I'll keep them in mind when I come back to it!