I've read that one very common postural defect - head forward rather than vertical over spine - comes from not breathing properly, not using the diaphragm. This was NOT in a journal, so I have no idea if it's true.

FWIW, that defect is common enough that it's built in to parts of our environments (e.g. car headrests that push forwards to accommodate drivers/passengers with this defect - and are uncomfortable for the rest of us).

Getting a bit more on subject...

>>As mentioned, I am trying to better shape my piano phrases with my breath.

If you've seen video of Glen Gould (known for his performance of the Goldberg Variations) it's clear he's doing this; he's practically singing.