ground back into action
Hi,
I came across this phrase while reading Harry Potter:
"Ron muttered, his teeth chattering, as the orchestra ground back into action and the ghosts swept back onto the dance floor."
According to Oxford, "grind" means "to break or crush something into small pieces" and the other definitions are similar or based on this original one, but all of them just don't make sense in this context. Could you please explain it to me? Thank you very much.