When I took up the challenge of upholstering a friend’s piano stool, it was quite a deviation from any leather work I’d attempted so far. In fact the only similarity was that it involved using leather, albeit chrome-tanned rather than the veg-tanned I’m familiar with. Chrome tanning produces a more supple hide which is more resilient to wear and staining, therefore more suitable for upholstery.
Lacking any knowledge in the art of upholstery, I enrolled on a beginners course at the Upholstery Skills Centre which proved to be very worthwhile.
The piano seat came with a solid ply base which makes for a much firmer seat cushion. It then becomes a compromise between providing sufficient padding and having a domed appearance. An alternative would be a 2” rectangular frame and creating the seat base with interwoven webbing.