Hi Karthik,
Sounds like a great project! Is the jazz music dataset also piano, or is it another instrument? If it's piano, the existing model might already do quite well, though it would be interesting to see what its shortcomings are and how it can be improved for a specific genre.
I think all of your ideas are worth trying. I'd be interested to hear whether training from scratch with a mix of datasets or finetuning from a checkpoint ends up working better. Because of the smaller size of your dataset, I think the big difficulty will be in how to get the model to train well for the specifics of that data without overfitting. I could see hparams related to dropout or model capacity helping there, as well as data augmentation (e.g., adding some noise or maybe even pitch shifting).
Best of luck with everything, and I'd love to hear how the project progresses!
-Fjord