I've found a number of posts on the internet where people have shared their diploma viva voce questions. These were really helpful for me when I was preparing, so though I would do the same while they're fresh in my mind. I think I did quite well on this section (better than I did on the recital )
Beethoven Romance in F
Sarabande and Gigue from Bach Partita 2
Dvorak 4 Romantic Pieces
De Falla Danse Espagnole arr Kreisler
1) How did you choose your programme? Were they pieces you particularly liked, for instance?
Followup - Wouldn't it have been more conventional to play the Bach first rather than the Beethoven? [implication: stick to chronological order for the programme]
2) You mentioned that there is speculation that Beethoven might have been intended as a 2nd movement of a concerto - why do you say that?
3) In your programme notes you say the Beethoven is in rondo form. Can you take us through this structure on the score?
Followup - Isn't F-minor [in the 2nd development section] a bit of a strange key to use at this point?
4) How does the modern violin differ from Bach's time?
Followup - Do you approach this music thinking about how Bach would have played it on a violin of the time, or do you think "this is my twenty-first century violin, let's make a twenty-first century sound"
5) How do you approach the question of memorisation?
6) You've mentioned the emotional aspects of Dvorak's music - tell us more about the emotions in this piece
7) Anything you'd like to add?
1) Variety of periods, moods. Arranged programme to vary emotional intensity, sandwiching sad/inward-looking with extrovert, ending with a big finish. Bach is inner movements of an inner partita in the cycle, much more inward-looking so started with more approachable Beethoven.
2) The Romance was a typical 2nd movement form at this point; Beethoven was in the habit of trying his hand at new genres of composition and only published when he was really happy with his work; there is an unfinished/fragmentary first movement in C
3) Highlighted the thematic material and where it returned and the significant key changes (particularly the lead toward the dominant and return to the tonic). F minor isn't conventional but used to good effect with emotionally intense writing
4) (all the obvious stuff about baroque violins). Music has changed so much since Bach's time that it's important to think about how it would have been approached in the 1720s
5) Talked about benefits of memorising (better communication, eye contact etc even if you are playing with music there); identified the risk of playing entirely without.
6) Didn't handle this one very well but muttered something about the 2nd movement (I had talked about this in my programme notes quite well but couldn't think of anything to add)
7) (they were keen to finish at this point as I had talked too much in my answers to 1 and 2) Talked briefly about how De Falla reconciles gypsy flamenco style with classical rules.
General observations: The questions were largely quite predictable from the reading I'd done, and were clearly led by things I'd mentioned in my programme notes. Also the examiners were lovely.