Good on you for taking on the FRSM! It's a very hefty programme with everything involved. And doing both the Chopin sonatas sounds awesome! I'd like to try and tackle those one day.
It's been a few years since I've done the exam so I had to look up the written submission guidelines. The syllabus states the following (I've highlighted the bits I thought were important):
In your Written Submission you are required to explore some of the content of your Recital programme and to focus in detail on a particular aspect or aspects surrounding the composition and performance history of one or more items of the chosen repertoire. You do not need to make reference to the whole programme. Appropriate areas for discussion might include issues about period and style or analytical approaches that illuminate interpretation. Other possible topics include issues of authenticity, reception history, the influence of wider cultural developments, the study of manuscript sources, the history of critical thought in relation to the repertoire, and the relationship between each work and its composer’s output. You might also wish to research the historical context of the chosen repertoire or the way in which a work exploits the particular idiom of the instrument/voice. The Submission should include personal insights and contain substantial evidence of critical evaluation and appropriate research. It should also reflect the preoccupations relevant to you as a performer as well as any issues that you take into account in your work. Above all, ABRSM would like to encourage candidates to think creatively about their Submission and to research a topic that focuses on an area of personal interest, i.e. not necessarily one covered in the suggestions given above. Trevor Herbert’s Music in Words (London: ABRSM, 2001) defines presentational conventions for written work, while also providing a basis for researching and writing at higher educational levels.Personally I would approach it by doing the following:
1. Learn and enjoy the sonatas.
2. Read up everything you can about Chopin (bios etc) and particular the sonatas. You could also ask yourself the following questions: How do the sonatas fit into the context of Chopin's other compositions? How do they fit into the context of the piano sonata? What were Chopin's influences at the time? What compositional/ harmonic devices are used in these works and his other works (esp the bigger works like the Ballads, Sherzos etc)?
3. Think of something you especially enjoy about Chopin's works and focus on that: like do you especially like his harmony? technical devices? ways he conveys emotion? The process of researching and writing this should be fun, so best to focus on an area that you enjoy or has special meaning for you.
Hope that's a help!
Here's a link to the ABRSM diploma PDF. The info on written submission starts on page 25. the 4500 words (+- 10%) don't include bibliography.
https://gb.abrsm.org/media/66252/performance-syllabus-final-sept-2021.pdfDon't hesitate if you have any other questions.
Kind regards
Dan