Primes

I wrote a movement in sonata form where all of the phrases in the exposition and development are prime numbers in length in terms of measures.

Primes.pdf

I listened to your piece and I admire your stamina and commitment in writing such a lengthy movement! However, I don't feel that its length is completely earned. A sonata form of 420 bars needs a really strong main idea if it's to retain the listener's attention and interest. Your folksy melody was pleasant, but if it were up to me, my first thought wouldn't have been to expand it into a large sonata-allegro form.

I also noted a sort of meandering quality to your lines that came from long phrases without a clear beginning or end. I think it's typically a good idea to write for string instruments in a similar way as one might write for voices or winds. Of course, strings have unique capabilities, but both the musicians and listeners will appreciate giving them space to "breathe." Chamber music especially, regardless of the musical language, is most naturally structured like a conversation.

I am also not sure that pandiatonicism is a good fit for sonata form without extra structural support. It's one of my preferred harmonic palettes, but without the "directionality" of functional tonality—or a rigorous approach to motives and pitch-class sets—it has the potential to sound a bit aimless. Since sonata form is essentially a teleological (goal-oriented) narrative, that directionality needs to be provided through other means, such as striking pitch contours, rhythmic drive, or strong motivic contrasts. As for the meter, I typically wouldn’t write a sonata form in 6/8, because of its lighter “dance” associations. But I’m sure it’s been done.

So all things considered, I would advise you to pursue greater concision in your presentation of ideas and find ways to articulate the structure of your piece more clearly on multiple levels. I am curious about what your creative process was for the movement: did you begin by planning the sections at a high level, or did you work mostly from beginning to end as you went?

It's all part of the process of finding your own voice. We're all in it with you! Good luck with your composing, and I'm eager to see where your creativity takes you!